COMPUTER HARDWARE AND DIGITAL ELECTRONICS SYSTEMS Unit- 1
Introduction to Computers Advantages Disadvantages Assembling Computer – Different parts computers Connecting various Devices and Components BIOS Setup –Load Fail Safe Default Load Optimized Default Standard CMOS Features Advance BIOS Features Advance Chipset Features BIOS Setup Integrated Peripheral Power Management Setup PnP PCI Configuration Frequency Voltage Control Supervisor User Password Setting Partitioning and Formatting HDD Introduction to file system Different types file system
Unit- 2
Input Devices Function Input devices– Keyboard Mouse Scanner MIC Light Pen and Touch Screen and their Components Output Devices Function output devices Monitor and Types monitors Speaker Printer and its types Inside to Printer and Plotter
Unit- 3
Memory Primary and Secondary Memory RAM and ROM and its types memory Packages and Modules SIP DIP SIMM DIMM RIMM’s Modules Installation Techniques Introduction the Cache Memory Types the Cache Memory Virtual Memory Flash Memory Secondary Storage Devices – FDD CD HDD DVD and their Internal Components and Structures installing different storage devices.
Unit- 4
Introduction to Electronics difference between electrical and electronics concepts current voltage résistance types current and their conversion different Types Electronic Components and their sub types soldering electronic components electronic tools switching circuits power electronics and digital electronics.
Unit- 5 -
Microprocessor BUS and It’s Types CPU Generation and X86 Intel family processor MHz and GHz. Identification Processor Different Parts Motherboard Processor Slot Socket Memory Slot Expansion Slot IDE Connector FDC connector COM Port Parallel Port USB BIOS Front panel connector Keyboard Connector Power connector Display connector Sound Port Ps 2 Connector
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UNIT - 1
INTRODUCTION
Computer
A computer is an electronic device that is designed to work with information. The computer takes information in, processes that information, and then displays the results. In this way, a computer is similar to a calculator, except that even the smallest computer is much more versatile than the most powerful calculator. Computers operate at amazingly fast speeds, with a typical computer processing millions of calculations every second.
A computer has four functions:
a. accepts data Input
b. processes data Processing
c. produces output Output
d. stores results Storage
Input (Data):
Input is the raw information entered into a computer from the input devices. It is the collection of letters, numbers, images etc.
Process: Process is the operation of data as per given instruction. It is totally internal process of the computer system.
Output: Output is the processed data given by computer after data processing. Output is also called as Result. We can save these results in the storage devices for the future use.
Computer System
All of the components of a computer system can be summarized with the simple equations.
COMPUTER SYSTEM = HARDWARE + SOFTWARE+ USER
• Hardware = Internal Devices + Peripheral Devices
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All physical parts of the computer (or everything that we can touch) are known as Hardware.
• Software = Programs
Software gives "intelligence" to the computer.
• USER = Person, who operates computer.
A computer is a device that you can use to store, manipulate, and display text, numbers, images, and sounds. Personal Computer
A personal computer is a small, relatively inexpensive computer that is designed for use by one person at a time. It allows you to perform personal tasks such as creating documents, communicating with other people, and playing games. The abbreviation PC is most often used to refer to computers that run the Microsoft Windows operating system, as well as to differentiate them from Macintosh computers.
Why Computer?
The word ‘Computer’ literally means to ‘Compute’ or to ‘Calculate’. Stated simply, it is an electronic device which processes information based on the instructions provided, to generate the desired output. It, therefore, requires two types of input – raw data, and the set of instructions to process or act upon the data. This can schematically be shown in Figure 1.1.
Outpu Data Process Output Instructions
Input
Figure: Processing Information Data can be of any type – text, numeric, alpha numeric, image, picture, sound etc. The instructions. 1 that act upon this data are also called the program or software in computer terminology.
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Advantages of Computers
Because of the many advantages of a computer, it has become an important household item. A computer operated by an individual without any specific computer operator is called a personal computer (PC). A PC can be a desktop or a laptop computer and can be used at home or at office. As per the requirement of the user, software is installed in a PC. Let's discuss the advantages of computers.
One can write more effectively by means of a computer. There are tools like spelling and grammar checker, thesaurus and dictionary, installed in the computer. Thus, it takes less time to proofread a written document and also, there is no need to open up a dictionary book to look for meanings of words. Typing is much faster than writing on a paper. If there is a need for reorganizing the sentences or paragraphs, one can cut and paste and make the necessary changes. Thus, overall a computer allows the user to create documents, edit, print, and store them so that they can be retrieved later.
Using a computer, one can remain connected to the world through Internet. Internet is a network of computers that communicates via the Internet Protocol Suite (TCP/IP). The World Wide Web (WWW) or simply web is a huge resource of information that can be accessed via the Internet. To mention a few of the resources, there are electronic mail (e mail), file transferring and sharing, online chat, and gaming. The Internet allows people from around the world to share knowledge, ideas and experiences in any field. But, there are both advantages and disadvantages of Internet.
E mail is a method of communication used globally and is provided with a system of creating, storing and forwarding mails. It may consist of text messages with attachments of audio visual clips. One can also download or upload files using the Internet. There are also facilities like online chatting available on the Internet. As compared to telephonic conversation, both e mail and online chat are cost saving. Online gaming is another important resource of the WWW. Many online games are available, which are of common interest for any age group. In addition, one can read current news, check weather conditions, plan vacations and make hotel and travel reservations, find out about diseases and treatment methods, conduct transactions, learn about specific countries and their cultures, seek jobs, buy products, etc via the Internet.
Nowadays, computers are widely used for education and training purposes. In schools, computer education has been made compulsory to spread awareness about computers. As a matter of fact, computers have become a learning tool for children. Also, there are many universities that provide online degrees, which is very advantageous for those people staying in the remote areas and for the disabled. In fact, online education is one of the most flexible and convenient forms of learning. One can take the benefit of such
4 | P a g e online degree programs staying at home without the need of relocation. Computers are also used for training purposes. Many companies use them to train their staffs.
However, in spite of the many advantages of computers, there are some disadvantages that cannot be ignored. The easy access to information via Internet has made students lazy in terms of their education since they are able to download information without exploring their topic of research. They also use computers for mathematical tables and calculations without actually solving the problems. Also, it is important for parents to keep a check on the browsing habits of their children as some websites are not meant for their viewing. Other disadvantages include identity theft and virus threat. Computers viruses are harmful to the systems and can be transferred from one computer system to another. Disadvantages of computer.
There are a lot of advandantages of using computer and it's necessary to handle it in our life. You can research so many information through the internet. When you do your homework, you can earily find some pictures and vidioes and you can use them as a reference. If you get used to use the computer, it's better to get a good job and in some companies, they insist us to get some certification about computer. So the importance of computer is becoming strengthen.
But some experts alert the danger of the computer addiction disorder. Especially for the children, they can be easily hooked on the computer games. Instead of doing homework, studying or playing with friends, they seclude and just play computer untill late at night. so they can concentrate the teacher's words and it destroys their schooling.
There is another problem of computer. Because of anonymity, some people can deceive other people and it might be a fraud. For example, there is a website where the people can post the advertisement and sell certain products. Throught that site, you paid for one dictionary. But when you recieve and open it, there is a brick, not the dictionary. Nowadays, the electronic commerce is getting popurlar, so it might happen like upper situaion.
When you use the computer a lot, it attacks your eye sight. The experts warn not to use the computer longer than 1 hour and after using it, you have to take a rest for your eyes. But people mostly use the computer longer than one hour and for the children, they can't easily refuse the temtation of computer.
Besides these, there are a lots of disadvantages such as illegal downloading and becomming violent. But the worst thing is that the computer addicts don't know what to do and they don't know how dangerous it is.
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Assembling Computer
Things to get in place before starting:
• Anti static wrist strap
• Set of screwdrivers and pliers
• Piece of cloth
• CPU Thermal compound (recommended)
• PC components
Tip: CPU Thermal compound is not a necessity but it is recommended to keep your CPU cool under load conditions by helping heat dissipate faster. It is a must if you intend to overclock your PC.
Note: You can find the meaning of an abbreviation at the end of this article under the heading Jargon Buster.
Step 1: Installing the motherboard
Make sure you have all the components in place and a nice, clean and big enough place to work with.
Put your antic static wrist strap on to prevent your components from getting affected. Make sure your hands are clean before starting. First we will be installing the motherboard which is a piece of cake to install.
• Open the side doors of the cabinet
• Lay the cabinet on its side
• Put the motherboard in place
• Drive in all the required screws
Tip: Most motherboards come with an antistatic bag. It is advisable to put the motherboard on it for some time and then remove it from the antistatic bag before placing it in the cabinet.
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Step 2: Installing the CPU
CPU is the heart of a computer so make sure you handle it properly and do not drop it or mishandle it. Also try not to touch the pins frequently so that they do not get dirty. Get hold of your motherboard and CPU manual. You need to place the CPU on the dotted white patch of the motherboard in a particular fashion for it to fit properly. There is a golden mark on the CPU to help you assist. Consult both your motherboard and CPU manual to see which position it fits exactly or you could also use try all the 4 positions.
• Lift the CPU lever on the motherboard
• Place the CPU properly on the motherboard
• Pull down the lever to secure the CPU in place
Warning: Do not try to push the CPU into the motherboard!
Got the thermal compound? Now is the time to use it. Take small amount of it and carefully apply it on the top surface of the processor. Be careful not to put it on the neighboring parts of the motherboard. If you do so clean it immediately using the cloth.
Tip: Thermal compounds should be changed once every six months for optimal performance.
Step 3: Installing the heat sink
After installing the processor we proceed to installing the heat sink. There are different kinds of heat sinks that are bundled with the processor and each has a different way of installation. Look into your CPU manual for instructions on how to install it properly.
• Place the heat sink on the processor
• Put the jacks in place
• Secure the heat sink with the lever
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After this you will need to connect the cable of the heat sink on the motherboard. Again look into the motherboard manual on where to connect it and then connect it to the right port to get your heat sink in operational mode.
Step 4: Installing the RAM
Installing the RAM is also an easy job. The newer RAMs ie. DDR RAMs are easy to install as you don’t have to worry about placing which side where into the slot. The older ones, SDRAMs are plagued by this problem.
If you want to use dual channel configuration then consult your manual on which slots to use to achieve that result.
• Push down the RAM into the slot
• Make sure the both the clips hold the RAM properly
Step 5: Installing the power supply
We will now install the power supply as the components we install after this will require power cables to be connected to them. There is not much to be done to install a PSU.
• Place the PSU into the cabinet
• Put the screws in place tightly
Tip: Some PSU have extra accessories that come bundled with it. Consult your PSU manual to see how to install them.
Step 6: Installing the video card
First you will need to find out whether your video card is AGP or PCI E. AGP graphics cards have become redundant and are being phased out of the market quickly. So if you bought a spanking new card it will certainly be a PCI E.
• Remove the back plate on the cabinet corresponding to the graphics card
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• Push the card into the slot
• Secure the card with a screw
• Plug in the power connection from PSU (if required)
High end graphics cards need dedicated power supply and if your graphics card needs one then connect the appropriate wire from PSU into the graphics card.
Step 7: Installing the hard disk
Hard disk is another fragile component of the computer and needs to handled carefully.
• Place the hard drive into the bay
• Secure the drive with screws
• Connect the power cable from PSU
• Connect the data cable from motherboard into the drive
If your hard drive is a SATA one then connect one end of SATA cable into the motherboard and other into the SATA port on the hard disk. If your hard disk is PATA type then use the IDE cable instead of the SATA cable.
Tip: If your PSU does not support SATA power supply then you will need to get an converter which will convert your standard IDE power connector to a SATA power connector.
Step 8: Installing optical drive
The installation an optical drive is exactly similar to an hard drive.
• Place the optical drive into the bay
• Drive in the screws
• Connect the power cable and data cable
Tip: When installing multiple optical drives take care of jumper settings. Make sure you make one as primary and other slave by using the jumper. This is not applicable if the drives are SATA drives.
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Step 9: Connecting various cables
First we will finish setting up internal components and then get on to the external ones. You will need to consult your motherboard manual for finding the appropriate port for connecting various cables at the right places on the motherboard.
• Connect the large ATX power connector to the power supply port on your motherboard
• Next get hold of the smaller square power connector which supplies power to the processor and connect it to the appropriate port by taking help from your motherboard manual
• Connect the cabinet cables for power,reset button in the appropriate port of the motherboard
• Connect the front USB/audio panel cable in the motherboard
• Plug the cable of cabinet fans
You are done with installing the internal components of the PC. Close the side doors of the cabinet and get it upright and place it on your computer table. Get the rest of the PC components like monitor, keyboard, mouse, speakers etc. which we will connect now.
• Connect the VGA cable of the monitor into the VGA port
• If mouse/keyboard are PS/2 then connect them to PS/2 ports or else use the USB port
• Connect the speaker cable in the audio port
• Plug in the power cable from PSU into the UPS
• Also plug in the power cable of the monitor
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You are now done with setting up your PC. Power on and see your rig boot to glory.
Step 10: Installing the OS and drivers
We are done with the hardware part. Now get your favorite OS disks ready and the CD that came with your motherboard.
• Set the first boot device to CD/DVD drive in BIOS
• Pop in the OS disk
• Reboot the PC
• Install the OS
• Install drivers from motherboard CD (applicable only to Windows OS)
Voila! You have your PC up and running. Enjoy your journey with your self assembled rig!
Jargon Buster
• CPU – Central Processing Unit
• RAM – Random Memory Access
• DDR Double Data Rate
• SDRAM – Synchronous Dynamic Random Access Memory
• PSU Power Supply Unit
• AGP – Accelerated Graphics Port
• PCI E – Peripheral Component Interconnect Express
• SATA – Serial Advanced Technology Attachment
• PATA Parallel Advanced Technology Attachment
• IDE – Integrated Drive Electronics
• ATX – Advanced Technology Extended
• USB – Universal System Bus
• VGA – Video Graphics Array
• PS/2 – Personal System/2
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• OS – Operating System
Different parts of computer
1. Mouse
2. Keyboard
3. Scanner
4. Digital Camera
5. Web Camera
6. Joysticks
7. Track Ball
8. Touch Pad/ Screen
9. Light Pen
10. Bar Code Reader
11. Microphone
12. Graphics Tablets Connecting various device and components
The computer system essentially comprises three important parts – input device, central processing unit (CPU) and the output device. The CPU itself is made of three components namely, the arithmetic logic unit (ALU), memory unit, and the control unit. In addition to these, auxiliary storage/secondary storage devices are used to store data and instructions on a long term basis.
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Central Processing Unit
Arithmetic Logic Unit Input Unit Output Unit Control Unit Main Memory
Secondary Storage
Figure: Schematic Representation of a Computer Computers are made of the following basic components: 1. Case with hardware inside: a. Power Supply The power supply comes with the case, but this component is mentioned separately since there are various types of power supplies. The one you should get depends on the requirements of your system. This will be discussed in more detail later b. Motherboard This is where the core components of your computer reside which are listed below. Also the support cards for video, sound, networking and more are mounted into this board. i. Microprocessor This is the brain of your computer. It performs commands and instructions and controls the operation of the computer. 1. Memory The RAM in your system is mounted on the motherboard. This is memory that must be powered on to retain its contents. 2. Drive controllers The drive controllers control the interface of your system to your hard drives. The controllers let your hard drives work by controlling their operation. On most systems, they are included on the motherboard; however you may add additional controllers for faster or other types of drives.
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2. Hard disk drive(s) This is where your files are permanently stored on your computer. Also, normally, your operating system is installed here. 3. CD-ROM drive(s) This is normally a read only drive where files are permanently stored. There are now read/write CD ROM drives that use special software to allow users to read from and write to these drives.
4. Floppy drive(s) A floppy is a small disk storage device that today typically has about 1.4 Megabytes of memory capacity.
5. Other possible file storage devices include DVD devices, Tape backup devices, and some others.
2. Monitor This device which operates like a TV set lets the user see how the computer is responding to their commands. 3. Keyboard This is where the user enters text commands into the computer. 4. Mouse A point and click interface for entering commands which works well in graphical environments. These various parts will be discussed in the following sections Hardware Vs Software
The electrical, electronic, mechanical and magnetic components that make up the computer system are together termed as ‘ hardware ’.These include components that are responsible for user input, display and mathematical processing. The CPU, disk drives, internal chips and wiring, modem, peripheral devices like the monitor, keyboard, mouse, printer, speakers etc. are together termed as computer hardware. Computer hardware cannot perform any manipulation or calculation without being instructed as to what to do and how to do it. Programs (or instructions) are required to tell the computer what to do. The generic term for computer programs is ‘ software ’. Software comes in two main types – system software and application programs.
System Vs Application software System software consists of programs that control the operations of the computer system itself. It consists of a group of programs that control the operations of a computer equipment including functions like managing memory, managing peripherals, loading, storing, and is an interface between the application programs and the computer. MS DOS (Microsoft’s Disk Operating System), UNIX are examples of system software. Software that can perform a specific task for the user, such as word processing, accounting, budgeting or payroll, fall under the category of application software. Such
14 | P a g e programs run on top of an operating system (like Windows, UNIX, Linux, Macintosh) and are used to carry out specific functions. Word processors, spreadsheets, database management systems are all examples of general purpose application programs.
BITS AND BYTES
All information in the computer is handled using electrical components like the integrated circuits, semiconductors, all of which can recognize only two states – presence or absence of an electrical signal. Two symbols used to represent these two states are 0 and 1, and are known as BITS (an abbreviation for BI nary Digi TS ). 0 represents the absence of a signal, 1 represents the presence of a signal. A BIT is, therefore, the smallest unit of data in a computer and can either store a 0 or 1. Since a single bit can store only one of the two values, there can possibly be only four unique combinations : 00 01 10 11 Bits are, therefore, combined together into larger units in order to hold greater range of values. BYTES are typically a sequence of eight bits put together to create a single computer alphabetical or numerical character. More often referred to in larger multiples, bytes may appear as Kilobytes (1,024 bytes), Megabytes (1,048,576 bytes), GigaBytes (1,073,741,824), TeraBytes (approx. 1,099,511,000,000 bytes), or PetaBytes (approx. 1,125,899,900,000,000 bytes). Bytes are used to quantify the amount of data digitally stored (on disks, tapes) or transmitted (over the internet), and are also used to measure the memory and document size.
BIOS or CMOS setup.
Issue
How to enter the BIOS or CMOS setup.
Solution
Note: This document doesn't help users who cannot enter BIOS or CMOS setup because of a password .
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Because of the wide variety of computer and BIOS manufacturers over the evolution of computers, there are numerous ways to enter the BIOS or CMOS Setup. Below is a listing of the majority of these methods as well as other recommendations for entering the BIOS setup.
New computers
Thankfully, computers that have been manufactured in the last few years will allow you to enter the CMOS by pressing one of the below five keys during the boot . Usually it's one of the first three.
• F1 • F2 • DEL • ESC • F10
A user will know when to press this key when they see a message similar to the below example as the computer is booting. Some older computers may also display a flashing block to indicate when to press the F1 or F2 keys.
Press
If your computer is a new computer and you are unsure of what key to press when the computer is booting, try pressing and holding one or more keys the keyboard. This will cause a stuck key error, which may allow you to enter the BIOS setup.
Once you've successfully entered the CMOS setup you should see a screen similar to the below example.
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Older computers
Unlike the computers of today, older computers (before 1995) had numerous different methods of entering the BIOS setup. Below is a listing of general key sequences that may have had to be pressed as the computer was booting.
• CTRL + ALT + ESC • CTRL + ALT + INS • CTRL + ALT + ENTER • CTRL + ALT + S • PAGE UP KEY • PAGE DOWN KEY
ACER BIOS
If your computer is unable to boot or you wish to restore the BIOS back to bootable settings and your computer uses an ACER BIOS, press and hold the F10 key as you turn on the computer. While continuing to hold the F10 key, you should hear two beeps indicating that the settings have been restored.
AMI BIOS
Older AMI BIOS could be restored back to bootable settings by pressing and holding the Insert key as the computer is booting.
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BIOS / CMOS diskettes
Early 486, 386, and 286 computers may have required a floppy disk in order to enter the BIOS setup. These diskettes are known as ICU, BBU, and SCU disks. Because these diskettes are unique to your computer manufacturer, you must obtain the diskettes from them. See the computer manufacturers list for contact information.
Early IBM computers
Some models of early IBM computers required that the user press and hold both mouse buttons as the computer was booting in order to enter the BIOS setup.
Other suggestions
Finally, if none of the above suggestions help get you into your CMOS setup you can cause a stuck key error, which will usually cause the CMOS setup prompt to appear and remain until you press a key to continue. To do this press and hold any key on the keyboard and do not let go (you may get several beeps as you're doing this). Keep holding the key until the computer stops booting and you're prompted with an option to enter setup or to press another key to continue booting.
Entering the BIOS Setup Program
The BIOS setup programs can normally be entered only during the boot process , either a cold boot or a warm boot (after hitting {Ctrl Alt Del}). Some setup programs will let you go into setup program using a key combination at any time.
At least one thing is finally becoming somewhat standard: the use of the {Del} key to enter the setup program during boot. This is true of AMI and Award BIOSes, and some others as well. Older BIOSes can use any of a myriad of strange key combinations, including {Esc}, {F1}, {F2}, {F10}, {Ctrl Esc}, {Alt Esc}, {Ctrl Alt Esc}, {Ctrl Alt Enter},
Typical Key Controls
Most setup programs show on the screen itself the keys to use to select and change various options; some instead use a very limited help screen, normally accessed with the F1 key. The following keys are pretty much universal:
• {Enter} is normally used to select a menu or sub area. • The arrow keys are used to move between settings (in rare cases, they are used to change the selected setting).
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• {Page Up} and {Page Down} or {+} and { } are the two most common pairs of keys for modifying the current setting. • {Tab} can also sometimes be used to move between sections or settings. • {Esc} is normally used to move up the menu hierarchy one level, and in some BIOSes it is used to quit out of the setup program as well.
The newer AMI BIOSes are graphical; you put a standard serial mouse on the first serial port and a faux Windows screen pops up with the settings in little "program groups". If you don't have a mouse or it isn't working, you can access this program using keys as well. (I tried it with a PS/2 style mouse once and it didn't work, strange that they wouldn't support this... could be that I did something wrong.)
Note: Some BIOSes have the ability to bypass some of the extended settings during boot, by holding down the {Ins} key during the boot process . This can be useful in the event that you make such incorrect settings that the BIOS cannot even boot (which can happen, though it takes talent. :^) ) Check your motherboard manual to see if your machine can do this
BIOS Settings
This section describes most of the BIOS settings that you will find in a typical Pentium class or higher PC. Some BIOS settings are quite universal, while others can be found on only the systems made with one type of BIOS or made by one manufacturer. This section lists the most common settings that are used in modern PCs, with full explanations as to what they are and how to set them. This includes the more common advanced settings, but does not attempt a "shotgun" coverage of every setting I've ever seen on a machine. Some are very atypical and usually not something you need to worry about. The less common a setting is, the more often it is the case that you really will want to leave it on its default setting anyway. Not always, but usually.
By the nature of how I designed this section, it should cover 95%+ of the settings in your BIOS that you will ever want to change. If you find a setting in your BIOS that isn't covered here, you may find it in the BIOS Survival Guide , which has a more complete list of the settings found on various types of PCs.
For each setting I describe the most common options and what they mean. In addition, I indicate which options are usually the default. I also describe what the implications are of using the different settings, and provide general recommendations on how to configure most of the parameters. The settings themselves are organized based on the names of the settings groups you will find in a typical BIOS setup program.
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Tip: It is a good idea to "back up" (record on paper) all of your BIOS settings once your PC is running and stable, and especially before you make any changes to them.
Tip: Reference this procedure for specific instructions on configuring the most important BIOS settings to safe values, to maximize the chances of booting a new or problematic system.
Note: Every setup program is slightly different from every other one. Even if two BIOSes are both on Pentium motherboards and are made by Award, they may have different settings. The commands as shown here might be different on your PC, or they might be in a different place. Use care when modifying these parameters, and refer to your motherboard manual if it is accurate.
Warning: The highly prudent will have a backup of their hard disk before fiddling with their BIOS settings.
Warning: Changing advanced parameters can lead to system instability and data loss. It is recommended that only users who really understand what they are doing change these settings. Proceed at your own risk.
Warning: If your BIOS contains a "hard disk utility" that includes items like setting interleave ratios, low level formatting , or "media analysis", do not use it on an IDE/ATA or SCSI drive (which includes virtually every PC hard drive made in at least the last 5 years). These old utilities are designed for the MFM and RLL drives from the 1980s and can in theory damage a modern drive, for which they are unnecessary. I wish they'd just take them out of the setup program entirely (and on many newer PCs they have)
BIOS Settings - Standard Settings
This settings group contains basic parameters that you will normally need to set (or adjust) for your system to work properly. Most of these are present on virtually every PC.
Date
The system date. Make sure that you enter it in the correct format; normally this is mm/dd/yy in North America, but may vary elsewhere.
Newer versions of Windows will let you change the date within the built in "Date/Time Properties" feature, and the BIOS date will be updated automatically by the system.
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Time
The system time. Most systems require this to be entered using a 24 hour clock (1:00 pm = 13:00, etc.)
Newer versions of Windows will let you change the time within the built in "Date/Time Properties" feature, and the BIOS time will be updated automatically by the system.
Daylight Savings
If your BIOS has this setting, enabling it will forward the time by one hour on the first Sunday in April, and drop it back by one hour on the last Sunday in October. The default value is usually "Enabled".
This setting is not present on most PCs; however, some operating systems, such as Windows 95, will do this for you automatically if you enable the daylight savings time option in their control settings.
Note: The date when daylight savings time "kicks in" can change in some cases; for example, a few years ago the spring date changed from the last Sunday in April to the first. If this happens again your BIOS will change the time on the wrong date so you will want to disable this unless a flash BIOS upgrade is made available to you that compensates.
DE Primary Master
This is where the hard disk parameters are entered for the primary master IDE/ATA device, the first drive in a modern IDE system. See the hard disk section for details on what these terms mean and how these devices are set up. The various settings for the drive are discussed in detail in the IDE Setup / Autodetection section . The default setting for this on a system with IDE autodetection, is usually "Auto".
Note: Some older systems only have places for two drives' parameters to be entered; often in this case they just call them "Drive C" and "Drive D"
IDE Primary Slave
This is where the hard disk parameters are entered for the primary slave IDE device, the second drive in a modern IDE system. See the hard disk section for details on what these terms mean and how these devices are set up. The various settings for the drive are discussed in detail in the IDE Setup / Autodetection section . The default setting for this on a system with IDE autodetection, is usually "Auto".
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DE Secondary Master
This is where the hard disk parameters are entered for the secondary master IDE device, normally the third drive in a modern IDE system (though it can be the second as well, if the primary slave device is not used). See the hard disk section for details on what these terms mean and how these devices are set up. The various settings for the drive are discussed in detail in the IDE Setup / Autodetection section . The default setting for this on a system with IDE autodetection, is usually "Auto".
IDE Secondary Slave
This is where the hard disk parameters are entered for the secondary slave IDE device, the fourth drive in a modern IDE system. See the hard disk section for details on what these terms mean and how these devices are set up. The various settings for the drive are discussed in detail in the IDE Setup / Autodetection section . The default setting for this on a system with IDE autodetection, is usually "Auto".
Floppy Drive A
The type of the first floppy drive . The choices normally are:
• 1.44 MB: A normal 3.5" drive. • 1.2 MB: A normal 5.25" drive. • 2.88 MB: A high density 3.5" drive, found on some newer systems. • 720 KB: A low density 3.5" drive. • 360 KB: A low density 5.25" drive. • None: No floppy drive present in the "floppy A" position. May read "not installed" or similar.
This setting usually defaults to a 1.44 MB 3.5" drive, the most common type currently in use.
Floppy Drive B
The type of the second floppy drive. See common choices under "Floppy Drive A" above.
The type of the second floppy drive . The choices normally are:
• 1.44 MB: A normal 3.5" drive. • 1.2 MB: A normal 5.25" drive. • 2.88 MB: A high density 3.5" drive, found on some newer systems.
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• 720 KB: A low density 3.5" drive. • 360 KB: A low density 5.25" drive. • None: No floppy drive present in the "floppy A" position. May read "not installed" or similar.
This setting usually defaults to "none" or "not installed" since most PCs don't have a second floppy drive.
Video Display Type
This is the standard type of the display you are using; almost always this should be set to either "VGA" or "VGA/EGA" for a modern PC, if you are using any sort of VGA or SVGA card (which is basically every PC made in the nineties.) This is also usually the default value.
Halt On
Some PCs give you the ability to tell the BIOS specifically which types of errors will halt the computer during the power on self test section of the boot process . Using this, you can tell the PC to ignore certain types of errors; common settings for this parameter are:
• All Errors: The boot process will halt on all errors. You will be prompted for action in the event of recoverable errors. This is the normally the default setting, and is also the recommended one. • No Errors: The POST will not stop of any type of error. Not recommended except for very special cases. • All But Keyboard: The boot process will stop for any error except a keyboard error . This can be useful for setting up a machine without a keyboard, for example for a file or print server. • All But Diskette/Floppy: All errors will halt the system except diskette errors. In my opinion, if your floppy drive has recurring and known problems, it is most likely best just to replace (or disconnect) the drive rather than using this.
Warning: Telling the system not to halt for any error types is generally not wise. You may end up missing a problem with your system that you will want to know about
BIOS Settings - Advanced Features
This section usually contains more advanced features for controlling the behavior of your system. There are some settings here that you will want to adjust to ensure
23 | P a g e maximum performance from your system. There may also be some features you will need to enable or disable if your system is exhibiting problem behavior .
Virus Protection / Virus Warning
This setting has one of the most misleading names of all of the parameters in the BIOS. The system BIOS really has no way at all to tell which programs are viruses, and which are "wanted" programs. If enabled, what this setting does is to trap any and all writes to the hard disk's master boot record , and display a message to the screen each time asking if you are willing to allow the write. Since one common type of virus is the boot sector infector , this can indeed prevent the spread of these viruses.
However, this setting will also cause the BIOS to display its warning message for any legitimate access to the boot sector . So if you use any utilities that modify partitions, or even if you reformat your hard disk, this message will pop up rather unexpectedly. You can of course just "authorize" the BIOS, telling it to proceed with the write, but this can grow rather annoying if it happens often. It can also be quite confusing to someone who doesn't understand what this strange BIOS message means.
Some people prefer the safety of having this enabled, others find it annoying and turn it off. In fact, most people don't regularly run utilities that modify the boot sector. If you turn this setting off, you can probably find a similar feature, more elegantly implemented, in a memory resident anti virus program .
Internal Cache
This setting enables or disables the internal cache on your processor. This is also known as the L1 or level 1 cache . For 486 or later processors this should be enabled; turning off the level one cache will lead to a major performance hit . Earlier processors don't have internal cache, and enabling this setting can possibly lead to problems. You should disable this setting only for testing purposes if you are trying to find a problem, or if you suspect a bad processor chip .
On some BIOSes you may see three choices: "Disabled", "Write Through" and "Write Back". These refer to the cache's write policy . The write back cache policy will produce the best performance .
External Cache
This setting enables or disables the external cache on your processor, also known as the L2 or level 2 cache. Most 486 or later motherboards include this cache memory. Like the internal cache setting, this should be enabled at all times unless you are
24 | P a g e disabling it for troubleshooting purposes. Disabling the external cache will cause your system to slow down dramatically, but you can use it if you are having system crashes and suspect a problem with the cache chips.
On some BIOSes you may see three choices: "Disabled", "Write Through" and "Write Back". These refer to the cache's write policy . The write back cache policy will produce the best performance .
Note: There are some motherboards out on the market, particular PCI-based 486 motherboards, that have fake level 2 cache on the board. One way to test for this is to disable the external cache and see if there is a performance decrease in the system. If there isn't, you never had any level 2 cache to begin with. In addition, some systems will report (in the System Configuration Summary ) the presence of enabled level 2 cache even when it is disabled. This is a BIOS that has been "doctored" and is a sign of fake cache on the motherboard as well. Amazing the trouble people will go to to cheat someone out of a few bucks, isn't it?
Quick Power On Self Test / Quick Boot
Enabling this setting will cause the BIOS power on self test routine to skip some of its tests during bootup . One of the key things this setting usually does when enabled is cause the POST to skip checking all of extended memory for errors.
Most people enable this setting to speed up the boot process , but you should realize that you do increase the chance of the POST missing an error if you use this. Fortunately (or unfortunately) the POST memory test is virtually useless to detect transient memory errors (as opposed to hard errors that you would discover the first time you powered up the machine with the new memory in it), so once your system is running and stable, you can in most cases enable this setting safely. It's still safest to leave it disabled, which is what I recommend unless you have truly monstrous amounts of RAM. After all, how often do you boot the system during normal use?
Memory Test Tick Sound
When enabled, the POST memory test will make a tick sound as it counts up your system memory. Most people leave this enabled, others turn it off because they find the sound annoying. Many newer systems skip this option and turn the sound off entirely.
When building a system, it is recommended that you enable this, as the sound will act as a confirmation that your speaker is working, and that the POST is progressing
25 | P a g e normally. This is important during the first few boots of a system, and also if you are having video problems.
Boot Sequence
This setting controls the order that the BIOS uses to look for a boot device from which to load the operating system during the DOS boot process . Older machines do not have this setting; they look at the floppy drive first (A:) and then the hard drive (C:). Most systems will at least let you choose between "A:, C:" (the default) and "C:, A:". Newer systems will allow you to boot from the CD ROM as well; in this case there will be six different combinations listed. The default will normally be "A:, C:, CD ROM".
Note: Booting off the second floppy disk , B:, has not been an option on any PC I've ever seen.
Some BIOSes are getting even more advanced in terms of the boot sequence options they will allow. Some systems will now allow you to boot off a different IDE hard disk than the primary master (C:), or let you boot from a SCSI device instead of IDE even when both are used in the same system (normally the IDE device gets preference ).
Changing the boot sequence to seek from the hard disk drive first instead of the floppy disk drive has some advantages, and also some disadvantages. There are two main advantages. First, if the floppy disk isn't bootable , you virtually eliminate the chance of a boot sector virus spreading to your hard disk from a floppy. Second, you have a measure of security and reliability since when the floppy disk is bootable, anyone can write their own system files and boot the PC with their floppy, bypassing the standard startup files on the hard disk.
The disadvantages of not having the floppy bootable all relate to convenience. First, if you ever do have a virus on your PC then you will normally need to boot from a clean floppy disk to disinfect your hard disk; you will have to go back into the BIOS and change the boot sequence, disinfect, and then change it back. Second, there are some software programs that require their own boot disks (though they are becoming quite rare). Third, if your hard disk ever fails, you won't have any way to boot the PC. Some viruses manifest themselves by making the hard disk disappear. Finally, if you are installing a new operating system, or building a PC, you really need to be able to boot from the floppy disk.
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S.M.A.R.T. for Hard Disks
Some BIOSes have a specific BIOS setting to enable monitoring of hard disks that support the SMART (Self Monitoring And Reporting Technology) feature , which can allow the hard disk to report, under some circumstances, impending failures of the hard disk. . The normal default for this setting is "Disabled".
Power On Delay / Boot Delay
If you have the combination of a PC that boots up quickly, and a hard disk that takes a relatively long time to spin up, your BIOS may start trying to boot the operating system before the hard disk is read. A giveaway to this problem is the computer that won't boot when first powered on but will boot seconds later if the reset button is pressed.
If your BIOS has this option, you can specify a time in seconds to delay the boot process . This is normally disabled, and should be unless you are experiencing this problem.
Boot Up Numlock Status
This setting, when enabled, automatically turns on your NumLock key when the system is booted. Most systems default this to enabled. This item is a matter of personal taste.
Tip: There is also a DOS command (NUMLOCK) that can be put in the CONFIG .SYS file to enable the NumLock key. This will override the BIOS setting at startup if used .
Swap Floppy Drives
A useful feature for those machines that use two floppy drives, when enabled this swaps the A: and B: drives. This enables you to change the bootable floppy without having to open the case and switch the cable. See here for details on multiple floppy drives and the floppy cable .
Warning: Windows NT 4.0 does not properly support the floppy drive swap BIOS option; do not enable it if using NT. I have read reports of people getting stuck in the middle of NT installs because NT changed the floppy disk letters in the middle of the installation.
Floppy Drive Seek
Causes the BIOS to search for floppy disk drives at boot time. When enabled, the BIOS will activate the floppy disk drives during the boot process: the drive activity light will
27 | P a g e come on and the head will move back and forth once. First A: will be done and then B: if it exists. When disabled, this seek will not be done. Older PCs always did this seek; on newer machines it can be disabled to speed up the boot process.
Note: This setting will not affect the boot sequence , and vice-versa; if the boot sequence starts with A: the system will still try to boot from the floppy disk even if this is disabled, and if the boot sequence starts with C: the system will still look to C: even if floppy disk seek is enabled.
Boot Up System Speed
There aren't as many PCs that have this setting any more. Usually the options are "High" and "Low", where "High" is the normal system speed, and is the default setting. "Low" is for debugging only. Overall, this is a software equivalent of the good old "Turbo Switch" and on a modern system should be used the same way: that is, not at all.
Keyboard Installed
Some BIOSes let you specify explicitly if there is a keyboard in the system. The default is of course "Installed" (or "Yes", etc.) If you are using a PC without a keyboard (for example, for a file server or secured network PC) this will instruct the BIOS to skip the keyboard test during the POST. Also see the "Halt On" setting for a different way to accomplish this task.
Typematic Delay
This setting controls the automatic repeat capability of your keyboard. Usually specified in milliseconds, this controls how long a key must be held down before it begins automatically repeating. Typical settings are usually somewhere between 200 and 1000 milliseconds. Use what feels comfortable. See also "Typematic Rate".
Note: Some higher-end keyboards have the equivalent function built-in.
Warning: Setting this too low can cause the keyboard to repeat keys during normal typing, which can appear to be "keyboard bounce" and imply a hardware problem with the keyboard to the casual user.
Typematic Rate
This setting controls the repeat rate for the keyboard when the typematic feature is activated. It is usually expressed in characters per second. Use what feels comfortable,
28 | P a g e but don't go too high or you may feed the characters faster than the system can deal with them, which can cause beeping or even system lockups.
Tip: Some higher-end keyboards have the ability to set this parameter built-in; sometimes it is called "Key Repeat" or "Repeat Rate".
Fast A20 / A20 Gate Option
In order to fully understand this setting you need to understand what the A20 line (21st address line) is and what its significance is . In a nutshell, the A20 line is used to control access to the high memory area, the first 64 KB or so of extended memory. This line is normally controlled by the keyboard controller . To improve performance , newer systems have this control function built into the chipset as well.
To have the chipset control the A20 line and improve performance, enable this option. This setting is normally enabled by default. There is rarely any reason to disable this.
Video BIOS Shadow
This parameter, when enabled, turns on BIOS ROM shadowing for the block of memory normally used for standard VGA video ROM code, which is C0000 to C7FFF (32K). See here for a full description of what ROM shadowing does ; in short, it speeds up your system by copying the contents of your video BIOS code from the slow ROM in which it resides into faster RAM.
The default for this setting depends on the particular system a great deal.. Enabling it will increase performance . Disable it if it causes system problems, particularly those related to the video subsystem.
Note: On some systems the video BIOS shadow setting is named for the address range the video BIOS occupies, C0000-C7FFFh, instead of being specifically called "Video BIOS Shadow".
System BIOS Shadow
When enabled, this parameter turns on BIOS ROM shadowing for the block of memory that contains your system BIOS. This is normally F0000 to FFFFF (64K). See here for a full description of what ROM shadowing does ; in short, it speeds up your system by copying the contents of your system BIOS code from the slow ROM in which it resides into faster RAM.
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This setting normally defaults to "Enabled". Since the system BIOS code is used so extensively, shadowing it can cause a great deal of system performance improvement.
C8000-CBFFF Shadow, CC000-CFFFF Shadow, etc.
Most BIOSes have several settings for shadowing each of the 16K blocks of RAM from C8000h through DFFFFh. These settings show up as something like "C8000 CBFFF Shadow", "CC000 CFFFF Shadow", etc., up to "DC000 DFFFF Shadow". Some systems have settings for ROM shadowing in 32K blocks instead of 16K, so you will see "C8000 CFFFF" instead of "C8000 CBFFF" and "CC000 CFFFF". (Some systems leave off the last digit in their notation, calling the blocks "C800 CBFF", etc. It's the same thing.)
When enabled, the setting selected turns on adapter ROM shadowing for that 16K block of memory. See here for a full description of what ROM shadowing does ; in short, it speeds up your system by copying the contents of any BIOS code found in adapters using this memory space, from the slow ROM in which it resides into faster RAM.
The areas of memory from C8000 to DFFFFh are normally used by expansion cards such as network adapters. Turning on shadowing would speed these adapters up in the same way that shadowing the system BIOS speeds up the system BIOS code. However, things are much more tricky here, because some adapters use RAM as well as ROM, and map this RAM into this address space as well. If they do, and you enable shadowing, the adapter will malfunction because shadowing write protects the RAM it uses (since it thinks it is emulating a ROM only, which cannot be rewritten). This can cause spurious results when using these cards, and can be very difficult to diagnose. In addition, normally unused areas of memory in this region are used as UMBs for loading drivers via the EMM386 driver, and enabling shadowing will cause this to malfunction.
For this reason, the default for shadowing these adapter ROM areas is normally "Disabled" and I recommend that it be left that way in most cases. If you know all the details on the card whose ROM you are trying to shadow, enabling this can in theory increase performance , but it is not going to be anything very substantial in most cases. Incidentally, on most IDE/ATA systems, the block from C8000 to CBFFFh is reserved by the IDE hard disk BIOS
BIOS Settings - Advanced Chipset Features
This section of the BIOS setup program provides settings to "tweak" the chipset control parameters. Most of these settings are associated with fine tuning control over the system cache, memory, and I/O buses, to optimize performance.
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Warning: This section contains many settings that have the potential to screw up your system. :^) If after reading these descriptions you are not sure what a setting does, it is usually best to leave it at its default setting . For most people, using some form of the automatic configuration setting is highly recommended.
Chipset Special Features / Global Features
Some chipsets have this "generic" setting that, when enabled, turns on some of the special performance enhancing features of the chipset. This should normally be enabled unless you experience lockups or other system problems.
I have thus far only encountered this setting on motherboards that use Intel's 430HX "Triton II" chipset .
Cache Timing
This setting determines the speed that the chipset will use for reading data from the external (level 2) cache . This normally appears as something like x y y y. In this case the parameter refers to the number of clock cycles to do a 32 byte burst read from the external cache line. Each entry in the cache of a modern PC is 256 bits wide; data is read from the cache using four consecutive 64 bit reads. The first read is normally slower than the others; this is the "x" above, and the next three reads are the "y"s. An example would be "3 1 1 1", which means it takes a total of six clock cycles to read from the cache. More information on cache timing can be found here .
In general, the lower these numbers, the faster your system will be. How low you can drop them depends on your system, how fast your memory is, what clock speed your memory bus runs at, etc. If your BIOS supports an "Auto" setting for this parameter, using it is normally wisest, although it may not produce the highest performance results . You can try more aggressive settings (lower numbers) but be prepared to back off if you experience system problems, and don't go below the rating for your cache type.
Level 2 Cacheable DRAM Size / Cache Over 64 MB of DRAM
This setting controls how much of the system memory is "covered" by the level 2 cache. Using uncached memory on your system can cause it to slow down dramatically . You should always ensure that this value is set at least as high as the total amount of RAM in your system. However, for best performance, do not set it any higher than it needs to be.
Many motherboards using the 430FX, 430VX and 430TX chipsets will not have this option; it is most common on 430HX motherboards to select between 64 MB and 512
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MB cacheability. You should in this case set it to 64 MB unless you are using more than 64 MB.
Note: This setting will not be present on Pentium Pro motherboards, since the Pentium Pro uses an integrated level 2 cache.
Level 2 Cache Size
Some systems have a specific setting you must change to indicate how much level 2 cache you have on your board. Most newer boards do not have this setting and instead the hardware automatically detects how much level 2 cache you have. If you have this setting in your setup program, make sure it is correct.
Note: This setting will not be present on Pentium Pro or Pentium II motherboards , since these chips use integrated level 2 cache, not cache on the motherboard.
System BIOS Cacheable
On most systems, you can shadow your system BIOS ROM . Shadowing increases performance by copying the BIOS code from ROM to much faster system RAM . Enabling this setting will allow the system to cache this RAM as well, further increasing performance.
Normally you will want to enable this unless you are having a problem with your system and turning it off fixes it. If you have system BIOS shadowing disabled, this setting will be ignored.
Video BIOS Cacheable
On most systems, you can shadow your system BIOS ROM . Shadowing increases performance by copying the video BIOS code from video adapter's ROM to much faster system RAM. Enabling this setting will allow the system to cache this RAM as well, further increasing performance.
Normally you will want to enable this unless you are having a problem with your system and turning it off fixes it. If you have video BIOS shadowing disabled, this setting will be ignored.
DRAM Parity Checking
When enabled, turns on parity checking for the system RAM . This should be enabled if you are using parity checking (or ECC), and disabled otherwise. The default is normally
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"Disabled" since (unfortunately) most modern systems don't use parity memory. I recommend the use of parity memory; see here for details on what parity memory is , and see here for a discussion of the merits of parity memory versus non parity memory .
Warning: If you turn on parity checking on a system that does not have parity memory in it, the system will halt with a parity error as soon as it tries to boot up. If you turn off parity checking on a system that does have parity memory, the system will run just fine, but you will have no parity checking protection active.
DRAM Parity / ECC Mode
On a system that supports both parity and ECC error detection / correction modes most newer systems support either both or neither selects which mode is activated. ECC stands for "error correcting code" or "error correction code" and is a more advanced error detection and correction protocol than straight parity.
The default for this setting is normally "Parity"; it is ignored or disabled if "DRAM Parity Checking" is disabled.
Single Bit Error Report
If you are enabling ECC on your system, the hardware is capable of detecting and correcting single bit errors on the fly. It is very useful to be able to know when this has happened, because if it happens often then this is a signal that you have a hardware or software problem in your PC. Enabling this option will cause the system to tell you when it corrects a single bit error when ECC is running. The default is usually "Disabled". I recommend enabling this if you are running with ECC enabled.
DRAM Speed / DRAM Timing / DRAM Auto Configuration
There are a number of settings that control the timing of your system memory . For a full discussion on system memory timing, look here . Most setup programs now come with some sort of "automatic" setting that will determine what these parameters are for you. This is a "parent" setting of sorts that can be used to control the other individual timing settings on the screen. These parent settings normally come in one of two flavors:
• Dynamic Automatic Timing Setting: Some BIOSes have a fully automatic setting. When you put the DRAM Timing setting on "Auto", the chipset will detect what type of memory and cache you have at boot time and dynamically set all the timings for you automatically based on what it finds. This is the simplest way to ensure basically good performance from your system using any type of memory that it supports.
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• Fixed Timing Based on Memory Speed: Other BIOSes, instead of having an "Auto" setting, let you choose from a selection of common memory speeds (or types) and then modify the individual timing settings based on your selection. Here, you may find settings like "70 ns", "60 ns", "EDO" and "Manual". "Manual" turns off the automated settings so you can tweak them yourself.
When you use the "Auto" setting (either fully automatic or by selecting a memory speed) the BIOS will normally "lock" the individual settings that are controlled by this one, to reflect the fact that they are being set automatically by the BIOS. To unlock the individual settings so you can change them, you normally must turn off the "Auto" setting, or select "Manual". The default in most BIOSes is to enable automatic timing settings.
Warning: In a system that dynamically sets timing based on the detected speed of your memory, you must take care when using memory of different speeds . You should generally put the slower memory in the first bank, often called Bank 0. Otherwise, the system may set the timing too fast for the slower chips.
DRAM R/W Leadoff Timing
This parameter controls how many clock cycles are required for the first access to memory during a four read "burst". In modern PCs, reads from the system memory are done in sets of four, because the level 2 cache used in the PC (which is filled by information from the main memory ) is 256 bits wide (four sets of 64 bits). The timing, in clock cycles, to perform this quadruple read is normally stated as "x y y y". The first read is slower because the address for the read must be supplied to the memory; the next three are faster because they are read consecutively from the first location (no need to supply an address).
Using the x y y y notation, the Leadoff Timing setting refers to the "x" value, the number of clock cycles for the first read. On most BIOSes, this parameter is absolute, and refers to the actual number of clock cycles used for the first access. On others, this setting is the number of additional cycles required for the first access. For example, let's suppose the optimal burst timing for your system is 5 2 2 2. This means the first read takes 5 clock cycles, and the next three take 2 each. In most BIOSes, Leadoff Timing would here be set to 5. In some BIOSes, you would have a parameter called "Leadoff Wait States" or "Additional Leadoff Cycles", and you would put here 3 (the number of additional cycles required for the first read.)
The lower this setting, the faster your system will work. How low you can set this depends on your memory bus speed and the speed and type of memory you are using.
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In general, the faster your memory bus runs the more cycles it will take to access the memory unless the memory is also made faster. Putting this setting too low will cause memory errors; some of these can appear intermittently and be very difficult to diagnose. Using automatic timing to set this parameter is usually recommended.
By default most BIOSes enable automatic timing settings so this parameter would be "locked out" and not changeable; if you enable manual timing settings this setting will usually default to the slowest possible setting at first, for compatibility reasons.
Note: This setting controls the timing for both reads and writes. Some systems could have two different settings instead, one for read leadoff timing and the other for write leadoff timing.
Note: This setting is normally controlled by the DRAM Timing or Auto Configuration mode, and if automatic settings are enabled you may not be able to change this
DRAM Read Timing / DRAM Burst Read Timing / DRAM Read Wait States
This parameter controls how many clock cycles are required for the burst reads from memory during a four read "burst". In most modern PCs, reads from the system memory are done in sets of four, because the level 2 cache used in the PC (which is filled by information from the main memory ) is 256 bits wide (four sets of 64 bits). The timing, in clock cycles, to perform this quadruple read is normally stated as "x y y y". The first read is slower because the address for the read must be supplied to the memory; the next three are faster because they are read consecutively from the addresses immediately following the first location (no need to supply an address)..
Using the x y y y notation, the Read Timing or Burst Read Timing setting refers to the "y y y" value, the number of clock cycles for the 2nd, 3rd and 4th reads of the four read cycle. This setting will most often have options like "x 2 2 2", "x 3 3 3" and "x 4 4 4", although in some BIOSes the single number is used instead ("2", "3", "4".) Some BIOSes, especially on older machines, instead refer to read "wait states", which is essentially the same thing, except that it is one less than the number referred to above. A wait state is an extra cycle inserted for the processor to wait for the system memory. In the x y y y notation, the "y" is the total number of cycles for each memory access. "x 1 1 1" is the best you can do, since it always takes at least one cycle. Zero wait states is the best you can do. So "x 3 3 3" is equivalent to 2 wait states.
Some chipsets will have a double value for this setting, with one used for EDO DRAM and another used for FPM DRAM. The system automatically detects which is being used; this is a sort of "semi automatic" setting. In this case you may see options that
35 | P a g e look something like "x 2 2 2 / x 3 3 3" or "x 3 3 3 / x 4 4 4 4". The first timing number is used when EDO is detected and the second when FPM is detected.
Your system will operate fastest when this setting is as low as possible. How low you can set this depends on your memory bus speed and the speed and type of memory you are using. In general, the faster your memory bus runs the more cycles it will take to access the memory unless the memory is also made faster. Putting this setting too low will cause memory errors; some of these can appear intermittently and be very difficult to diagnose. Using automatic timing to set this parameter is usually recommended.
By default most BIOSes enable automatic timing settings so this parameter would be "locked out" and not changeable; if you enable manual timing settings this setting will usually default to the slowest possible setting at first, for compatibility reasons.
Note: This setting is normally controlled by the DRAM Timing or Auto Configuration mode, and if automatic settings are enabled you may not be able to change this.
Note: On some BIOSes this setting is combined with DRAM Write Timing / DRAM Write Burst Timing. In this case the same timing is used for both reads and writes
DRAM Write Timing / DRAM Burst Write Timing / DRAM Write Wait States
This parameter controls how many clock cycles are required for the burst writes to memory during a four read "burst". In most modern PCs, writes to the system memory are done in sets of four, because the level 2 cache used in the PC (which is filled by information from the main memory ) is 256 bits wide (four sets of 64 bits). The timing, in clock cycles, to perform this quadruple write is normally stated as "x y y y". The first write is slower because the address for the write must be supplied to the memory; the next three are faster because they are written consecutively to the addresses immediately following the first location (no need to supply an address). Memory system timing is discussed in much more detail here .
Using the x y y y notation, the Write Timing or Burst Write Timing setting refers to the "y y y" value, the number of clock cycles for the 2nd, 3rd and 4th writes of the four write cycle. This setting will most often have options like "x 2 2 2", "x 3 3 3" and "x 4 4 4", although in some BIOSes the single number is used instead ("2", "3", "4".) Some BIOSes, especially on older machines, instead refer to write "wait states", which is essentially the same thing, except that it is one less than the number referred to above. A wait state is an extra cycle inserted for the processor to wait for the system memory. In the x y y y notation, the "y" is the total number of cycles. "x 1 1 1" is the best you can
36 | P a g e do, since it always takes at least one cycle. Zero wait states is the best you can do. So "x 3 3 3" is equivalent to 2 wait states.
Note: Systems that have a double value for read burst timing (one for EDO memory and one for FPM ) will still have just a single value for write burst timing. This is because EDO is only faster than FPM memory when reading.
Your system will operate fastest when this setting is as low as possible. How low you can set this depends on your memory bus speed and the speed and type of memory you are using. In general, the faster your memory bus runs the more cycles it will take to access the memory unless the memory is also made faster. Putting this setting too low will cause memory errors; some of these can appear intermittently and be very difficult to diagnose. Using automatic timing to set this parameter is usually recommended. By default most BIOSes enable automatic timing settings so this parameter would be "locked out" and not changeable; if you enable manual timing settings this setting will usually default to the slowest possible setting at first, for compatibility reasons.
Note: This setting is normally controlled by the DRAM Timing or Auto Configuration mode, and if automatic settings are enabled you may not be able to change this.
Note: On some BIOSes this setting is combined with DRAM Read Timing / DRAM Read Burst Timing. In this case the same timing is used for both reads and writes.
DRAM Speculative Leadoff
This is a performance enhancement available with some chipsets to speed up the (relatively slow) first access to system memory. In short, the memory controller "cheats" by starting the initial read request before the address for the read has been completely resolved. This can result in a performance increase. For best efficiency you will normally enable this. If doing so causes instability then you should disable it.
Note: This setting is normally controlled by the DRAM Timing or Auto Configuration mode, and if automatic settings are enabled you may not be able to change this .
Turn-Around Insertion
When enabled, inserts an extra clock cycle (wait state) between consecutive DRAM read cycles (i.e., consecutive 4 read bursts). Normally the system can perform back to back burst reads without this extra delay, and the default for this setting is "Disabled".
Note: This setting is normally controlled by the DRAM Timing or Auto Configuration mode, and if automatic settings are enabled you may not be able to change this.
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Memory Hole
Some (unusual) expansion cards require access to particular memory addresses in order to function properly. This parameter lets you set aside the appropriate area of memory for these cards. The typical memory areas that can be set aside are "512 640KB" (the upper 128K of conventional memory) and "15 16MB".
This setting should be disabled unless you have a card that you know requires this setting. The default is normally "Disabled".
ISA (or AT Bus) Clock Speed / Divisor
This setting controls the speed of the ISA bus , in one of two ways. The less common way is for the setting to allow a direct setting of the ISA clock speed; this would include options of "6 MHz", "8 MHz", etc. The most common way is for the ISA clock speed to be set as a fraction of the PCI clock speed. The settings in this case will usually look something like "PCICLK/3", "PCICLK/4", "PCICLK/6", etc.
The setting to choose is the one that puts the ISA clock speed as close as possible to 8.33 MHz, which is the accepted standard maximum clock speed for the bus. Anything higher than this is considered overclocking. 8.33 MHz means that the correct option for a 33 MHz or 30 MHz PCI machine would be "PCICLK/4", while for a 25 MHz PCI machine it would be "PCICLK/3".
On some BIOSes there is an "Auto" setting as well that will pick the right fraction depending on the PCI bus speed it detects, but this is somewhat less common in my experience than other automatic settings elsewhere in the BIOS.
8-Bit I/O Recovery Time
This setting allows you to insert additional clock cycles after an 8 bit ISA I/O request. These are sometimes needed to slow down the processor after completing activity on the ISA bus, which runs much slower than the PCI bus. The default setting for this is usually 1 cycle. This can normally be increased to 5 or higher, or reduced to 0 (disabled). Normally you will want to keep this at its default setting.
16-Bit I/O Recovery Time
This setting allows you to insert additional clock cycles after a 16 bit ISA I/O request. These are sometimes needed to slow down the processor after completing activity on the ISA bus, which runs much slower than the PCI bus. The default setting for this is
38 | P a g e usually 1 cycle. This can normally be increased to 5 or higher, or reduced to 0 (disabled). Normally you will want to keep this at its default setting.
Peer Concurrency
This setting, when enabled, allows multiple PCI devices to be active at the same time. The default for this setting is "Enabled" and you will normally want to leave it on the default.
BIOS Settings - PCI / PnP Configuration
The settings in this section deal specifically with the PCI bus and Plug and Play (PnP) settings. PCs that do not have a PCI bus will of course not have this section at all; older buses such as the VLB did not have the features that this section of settings controls. The PCI bus for the most part takes care of itself, but the settings in this section can be used when particular behavior by the bus or expansion cards needs to be addressed.
Warning: This section contains many advanced settings that in the vast majority of cases you do not need to change. For most users, using some form of the provided automatic configuration setting is highly recommended.
Plug and Play Aware OS
This setting is shown on only some BIOSes. If present, enabling this tells the BIOS that you are using an operating system that supports the Plug and Play specification (such as Windows 95). When enabled, the BIOS will look for and initialize any Plug and Play cards in the system. Enable the setting if using Windows 95 or another Plug and Play compatible OS. The default is normally "Disabled".
Note: Some BIOSes will perform the initialization of Plug and Play cards automatically regardless of the operating system being used, and will thus not have this setting. Some will work fine with Plug and Play regardless of how this option is set. However, on some systems that have this setting, Plug and Play may not function properly if the setting is disabled.
PCI IDE Bus Master
Some BIOSes have an explicit setting to enable bus mastering of PCI IDE hard disk drives. If this setting is present in your BIOS and you are using PCI IDE bus mastering you should set this to "Enabled". Otherwise it should be left on the default, which is "Disabled".
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Automatic Resource Allocation
There are several settings in the PCI / PnP Configuration section of the BIOS program that deal with assigning interrupt resources. This includes both regular IRQs and the internal PCI interrupt resources. For most applications there is no need to manually select or deal with these resources; in this case the default setting of "Auto" should be selected, to enable automatic resource allocation. Not all BIOSes have this setting.
When you use the "Auto" setting the BIOS will normally "lock" the "PCI IRQ and DMA Settings" (below) to reflect the fact that they are being set automatically by the BIOS. To unlock the individual settings so you can change them, you must turn off the "Auto" setting.
PCI IRQ and DMA Settings / IRQ
When automatic resource allocation is not used, the BIOS allows you to specifically designate which system interrupts (IRQs) and direct memory access channels (DMAs) you want it to be able to use for setting up Plug and Play devices. For each IRQ or DMA, except ones reserved by the system, you can designate either "PCI/PnP" or "ISA /Legacy". When a resource is assigned to "ISA/Legacy" it is declared "off limits" to the BIOS.
The IRQs that you can normally set here are IRQs 3, 4, 5, 7, 9, 10, 11, 12, 14 and 15. The DMA channels are 0, 1, 3, 5, 6 and 7. (The others are reserved by system devices.) The default on most systems for each of these settings is "PCI/PnP". If your system does not have automatic resource allocation (which is preferred) then it is usually best to leave these settings on "PCI/PnP" unless you are having a problem with Plug and Play. For example, if PnP keeps taking a resource for a PnP card that you need for an ISA card, you might want to set that resource to "ISA/Legacy " here to reserve it.
Note: If automatic resource allocation is enabled, these options will normally either be locked to prevent change, or even cleared from the screen altogether, since the BIOS will control them automatically.
1st / 2nd / 3rd / 4th Available PCI Interrupt
The PCI bus uses its own internal interrupts , usually numbered #1 to #4 or #A to #D. Some PCI cards need to be able to use one of the regular system IRQs (interrupt request lines) to communicate with the processor. This setting "maps" the PCI interrupts to regular system IRQs by telling the BIOS which regular interrupt line to use for PCI cards that need one. The usual choices for this are IRQ9, IRQ10, IRQ11 and IRQ12.
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Note: If automatic resource allocation is enabled, these options will normally either be locked to prevent change, or even cleared from the screen altogether, since the BIOS will control them automatically.
PCI VGA Palette Snoop
The VGA "palette" is the set of colors that are in use by the video card when it is in 256 color mode. Since there are thousands of colors and only 256 can be used in that mode, a palette containing the current colors is used . Some special VGA cards, high end hardware MPEG decoders etc. need to be able to look at the video card's VGA palette to determine what colors are currently in use. Enabling this feature turns on this palette "snoop".
This option is only very rarely needed. It should be left at "Disabled" unless a video device specifically requires the setting enabled upon installation.
BIOS Settings - Power Management
This section contains the various settings that you can use to control your system's automatic power management settings. The pros and cons of using it are in this section on system care .
Note: In many ways, automatic power management is still "not ready for prime time", at least in my experience. Enabling power management can cause problems in your system because many software programs aren't prepared to properly deal with having the processor power down or the hard disks turn off, etc. You can certainly use power management, but be prepared to disable some of the settings if you have problems with them. I strongly recommend disabling all power management features when initially assembling a new system or performing upgrades or new software installations. If you do not, you will have a hard time figuring out what is causing any problems you might experience.
Global Power Management Setting
This is a setting that, if present, globally enables or disables power management. When set to "Disabled", the other settings in this section will typically be either locked out (so they cannot be changed) or else they will simply be ignored.
Video Power down Mode
If present, this setting controls the method used to put the monitor into low power mode. The typical options for this setting are:
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• DPMS: Select this option if your monitor supports the DPMS standard for monitor power management . This is the preferred and usual default setting; most modern monitors do support DPMS. • V/H Sync+Blank: Selecting this option causes the video card to shut down the vertical and horizontal sync signals to the monitor, as well as sending blank data to the monitor. • Blank Screen: This option causes the monitor to be blanked only.
Video Power Down Timeout
This setting controls how long the system must be idle for the video to be powered down. It is specified in minutes, or set to "Disabled". How long you set this for depends on your personal taste and how you use your system. Note that a colorful "screen saver" really doesn't save any power at all over regular use of the monitor the monitor is still on and displaying information either way.
Hard Disk Power Down Timeout
This setting controls how long a hard disk must be left idle before it spins down. The default is "Disabled". In a system with more than one hard disk, an idle timer is normally maintained individually for each. The choice of setting here depends a lot on how you use your system, as well as your personal opinion on the question of whether or not hard disks are better off running continuously or spinning down when not in use.
Doze Mode Timeout
This setting defines the number of minutes before the system enters "doze mode", the first level of system inactivity shutdown. The exact definition depends on the system, but in general this mode means that the processor slows down to a minimal activity level while other parts of the system keep running as normal. The default for this setting is usually "Disabled".
Standby Mode Timeout
This setting defines the number of minutes before the system enters "standby mode", the intermediate level of system inactivity shutdown. The exact definition depends on the system, but in general this mode means that the processor slows down to an even lower activity level than doze mode, and the video and hard disk drives are powered down. The default option is "Disabled".
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Suspend Mode Timeout
This setting defines the number of minutes before the system enters "suspend mode", the deepest level of system inactivity shutdown. The exact definition depends on the system, but in general this mode means that all system devices are shutdown (except for any that the BIOS is specifically told to keep running) and the processor is shut down to a trickle mode. The default option is "Disabled".
IRQ Wake-Up Events and Activity Monitors
When the system enters a power down mode, it will look for activity to tell it when to wake back up. Normally you wake the system back up either by pressing a key or moving the mouse. However, you may want the system to wake up in response to other events. For example, you might want the system to wake up when activity on the modem is detected, if your PC answers incoming faxes. Some BIOSes give you the ability to specify whether or not activity on an IRQ will wake up the system.
The BIOS monitors the system for "activity" to determine when to enable power management. You can tell the system what it should consider activity and what it should not, in other words, what sorts of events on the PC should reset the idle counter for power management. For example, in almost every case a movement of the mouse or a keypress could be considered activity. However, if you have a sensitive mouse that can move slightly in response to vibration, you might want to set the BIOS so that movement on the mouse will not reset the power management countdown timers.
There will normally be a separate setting for each IRQ. For each one, the options will typically be:
• Wake Up: Activity on this IRQ will wake up the system when in a power down mode. • Monitor: Activity on this IRQ will reset the system idle countdown timers. • Both: Activity on this IRQ will both wake up the system when powered down and reset the idle timers when powered up. • Neither: Activity on this IRQ will neither wake the system nor reset idle timers.
The default for these depends on the system. Some BIOSes use similar controls with different names, or may separate the wake up event controls from the monitoring controls. If you are using power management you will want to tailor these based on what interrupts (devices) are in use on your system. Look here for information on what the typical IRQ allocations are on a PC .
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Tip: For a system with a PS/2 style mouse, the mouse will be on IRQ 12. For a system with a serial mouse, the mouse will be on whatever IRQ is assigned to the COM port the modem is using. This is usually COM1, which uses IRQ 4.
Note: IRQ1, which is generated by the keyboard, is not usually listed here as it always causes a wake-up from power management, and cannot normally be disabled.
BIOS Settings - Integrated Peripherals
This section discusses settings that control your system's integrated peripherals. These settings are used to enable or disable integrated peripheral support, and set the various resources they use. If in addition to the standard integrated peripherals (serial and parallel ports , floppy and disk drives, etc.) you have integrated video, sound or other devices, you may find controls for them in this section.
Integrated Floppy Disk Controller
This setting enables or disables the integrated floppy disk controller (FDC). The default for this is "Enabled". If for some reason you are using a plug in floppy disk controller card, you will want to disable the integrated controller.
Integrated IDE Controllers
This setting enables or disables the integrated primary and secondary IDE/ATA controllers . If you are using an add in IDE controller card (which there is normally no need to do), or if you are not using IDE devices at all (for example, if you use SCSI devices), you can disable the built in controller here.
On some BIOSes a single setting controls both the primary and secondary channels; the options in this case are "Disabled", "Primary", "Secondary" and "Both". Other BIOSes have two separate "Enabled"/"Disabled" settings, one for the primary channel and one for the secondary channel.
The default on most systems is to enable both IDE channels. This is usually an acceptable setting for most PCs, but some systems can exhibit strange behavior if the secondary IDE channel is enabled but there are no drives on it; for example, Windows 95 may try to set up a drive controller device on the secondary channel and then get confused when nothing is on it. It is therefore prudent to disable the secondary IDE channel unless you are using it. This will also free up the IRQ used by the secondary channel (IRQ15) for use with other devices, if you need it.
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Integrated Serial Port 1 / Serial Port 2
This setting lets you specify the resources for the first and second serial ports on the motherboard. The exact name used for the various options varies (some call them "COM1", "COM2", etc. while others just list the I/O address and IRQ options). For each serial port setting you will typically find these:
• 3F8/IRQ4 (COM1): Sets the serial port to the I/O address and IRQ normally used by COM1. This is usually the default for the first serial port. • 2F8/IRQ3 (COM2): Sets the serial port to the I/O address and IRQ normally used by COM2. This is usually the default for the second serial port. • 3E8/IRQ4 (COM3): Sets the serial port to the I/O address and IRQ normally used by COM3. • 2E8/IRQ3 (COM4): Sets the serial port to the I/O address and IRQ normally used by COM4. • (Other options): Some systems now let you select other IRQs to assign to the onboard ports, to use if you are trying to avoid a resource conflict. • Disabled: Disables the serial port.
Normally you will set the first serial port to the resource settings for COM1, and the second to COM2. If you are using an internal modem and you want it to be set up by your system as COM2, the easiest way to do this without generating any conflicts is to disable the second serial port here, to prevent interference.
Integrated Parallel Port
This setting lets you specify the resources for the integrated parallel port. On most systems you are allowed to choose one of the typical resource settings allocated to parallel ports, or to disable the port:
• 378/IRQ7 (LPT1): Sets the parallel port to the I/O address and IRQ normally used by LPT1. This is usually the default. • 278/IRQ5 (LPT2): Sets the parallel port to the I/O address and IRQ normally used by LPT2. • Disabled: Disables the integrated parallel port.
Integrated Parallel Port Mode
Parallel ports have several different modes of operation. The original parallel ports were used only for one way communication from the PC to the printer; newer ones include bi directional communication and other abilities. The normal choices for this setting are:
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• SPP: Sets the parallel port to function as a Standard Parallel Port. This is the default (and slowest) option. • EPP: Sets the parallel port to Enhanced Parallel Port mode. Sometimes also called "Bi directional" • ECP: Sets the parallel port up as an Enhanced Capabilities Port. This setting requires the use of a DMA channel, usually specified through another BIOS setting .
Generally speaking, you will usually want to use EPP or ECP. ECP has enhanced performance but greater compatibility problems, overall. I usually use EPP.
Note: This setting is either locked out or ignored if the parallel port is disabled.
Parallel Port ECP DMA Channel
If your system supports ECP parallel port mode and you have the port set to use ECP, you must use this setting to assign a DMA channel for use by the port. The usual options are "DMA 1" and "DMA 3".
Note: This setting is either locked out or ignored if the parallel port is disabled, or if the parallel port mode is not set to ECP.
Warning: Some BIOSes allow this to be set to DMA channel 2 as well, which is normally reserved for the floppy disks. This will often create a resource conflict if chosen.
PS/2 Mouse Enable
On systems that support a PS /2 style mouse, this setting enables or disables this port. If you are using the port you should enable this, otherwise you should disable it so that the interrupt reserved for the PS/2 mouse (IRQ12) can be used for another purpose. Some systems have an "Auto" setting for this parameter, which is really ideal, since it will only enable PS/2 support if you actually have one connected.
USB Enable
Use this setting to enable USB (Universal Serial Bus) devices on motherboards that support USB. If you are not using USB, leave this setting at its default ("Disabled").
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BIOS Settings - Security / Password Settings
This section lets you set security passwords to control access to the system at boot time and/or when entering the BIOS setup program. Some systems have a single password, while many newer ones now have two: a supervisor and a user password.
Warning: If you set a password on your system, make sure you write it down in at least two places. If you lose the password you will be locked out of your own system, and then you will have to resort to techniques like these . :^) For most users, a password is unnecessary. In a shared office environment, it can be very helpful however, to control access to the PC.
Supervisor Password
Select this option to set the supervisor password. The supervisor password is the higher level password of the two normally present on the system. On most systems, when the supervisor password has been set, it must be entered in order to access the BIOS setup program, or to change the user password.
User Password
Select this option to set the user password. The user password is the lower level password of the two normally present on the system. The user password usually allows the system to be booted, but does not allow access to the BIOS setup program. The supervisor password must be used to enter the BIOS setup program.
Note: On some systems, either the supervisor or user passwords will allow access to the BIOS setup program. In this case the existence of two passwords may be to allow a single password to be set up for an administrator, which will work for multiple machines, while the user password is individual for each machine.
BIOS Settings - Hardware Device Settings / "CPU Soft Menu"
The newest rage in motherboard design is the so called "jumperless" motherboard. While this name is an exaggeration these boards do have jumpers , just fewer of them than a regular motherboard the idea is sound: to move many of the low level hardware selection functions from hardware jumpers to regular BIOS settings, accessed through a BIOS settings group sometimes called a "CPU soft menu". Abit has popularized this type of motherboard.
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This section describes the settings that are found in this setup group on jumperless motherboards. Regular jumpered motherboards will of course not have a section of this sort in their BIOS setup.
Warning: Setting the values in this section incorrectly can possibly damage your processor or other hardware.
CPU Name/Type
The BIOS will automatically detect and display the type of CPU in the PC, including the manufacturer and family name (e.g., "Intel Pentium", "AMD K6"). This value cannot be changed.
CPU Operating Speed
This setting allows you to select the operating speed of your processor directly. When you set this value, the BIOS will automatically set the "External Clock" and "Multiplier Factor" values for you, and lock them so they cannot be changed. For example, setting this value to "166" will set the external clock to 66 MHz, and the multiplier to 2.5X. To manually control the external clock and multiplier factor values, you must set this parameter to "User Defined".
External Clock
This setting controls the clock speed of the memory bus on the motherboard, and is normally 50, 60, 66 or 75 MHz. The internal processor speed is the product of the external clock speed of the motherboard and the multiplier used by the processor.
Note: When the CPU Operating Speed parameter is set to a specific number, the External Clock parameter is computed by the BIOS and this setting is disabled.
Multiplier Factor
This setting controls the multiplier that is used to determine the internal clock speed of the processor relative to the external or motherboard clock speed. The usual values are 1.5X, 2X, 2.5X, 3X, 3.5X and so on.
Note: When the CPU Operating Speed parameter is set to a specific number, the External Clock parameter is computed by the BIOS and this setting is disabled.
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CPU Power Plane
This setting controls how the voltage for the processor is to be specified. There are three different options. Depending on which one you select, the BIOS will change the other available voltage settings:
• Single Voltage: This option is, of course, for conventional processors that use a single voltage only. Selecting this option enables the "Plane Voltage" setting and disables the other voltage settings. • Dual Voltage: Select this option for processors that use split rail or dual voltage. This option enables the "I/O Plane Voltage" and "Core Plane Voltage" settings. • Via CPU Marking: Selecting this option will allow you to specify the CPU marking (specification) code for your processor, which will tell the BIOS how to set the voltage automatically. This is done using the "CPU Marking" BIOS setting, and the other voltage settings are disabled. The code is usually a five character code such as "SY016" that is found on the top surface or bottom surface of the CPU.
Plane Voltage
When the CPU Power Plane is set to "Single Voltage", this parameter allows you to choose what the voltage should be. This should be set to the correct voltage for your particular CPU . When CPU Power Plane is set to anything other than "Single Voltage", this setting will not be present.
I/O Plane Voltage
When the CPU Power Plane is set to "Dual Voltage", this parameter allows you to choose what the I/O or external voltage should be. When CPU Power Plane is set to anything other than "Dual Voltage", this setting will not be present.
Core Plane Voltage
When the CPU Power Plane is set to "Dual Voltage", this parameter allows you to choose what the core or internal voltage should be. When CPU Power Plane is set to anything other than "Dual Voltage", this setting will not be present.
CPU Marking
When the CPU Power Plane is set to "Via CPU Marking", this parameter allows you to choose what the marking code is for your CPU, which will tell the BIOS what voltage(s) the CPU requires. You may not know what your code is, or it may not be listed, so you
49 | P a g e may want to use the manual settings ("Single Voltage" or "Dual Voltage") in this case. When CPU Power Plane is set to anything other than "Via CPU Marking", this setting will not be present.
BIOS Settings - Auto Configuration and Defaults
In addition to the automatic configuration options offered in several specific areas of the BIOS setup (memory timing, hard disk autodetection, etc.) most BIOSes also offer a menu selection to automatically set all options in the BIOS to predefined settings.
Note: Auto configuration selections will not generally replace the settings in the Standard Setup section, in order not to wipe out any specific settings you have entered for your floppy or hard disk drives, or the current date and time .
Warning: It is prudent to record your system's current settings on paper before loading any default settings so that you know what you have changed and can undo the automatic settings if necessary. You may also find it useful to reference this procedure to help set your key settings again after doing a default load
Auto Configuration with BIOS Defaults / Failsafe Settings
Select this option to replace most of the current BIOS settings with predefined settings (coded into the BIOS) that are intended to put the system into as stable a state as possible. This means in most cases the slowest memory timings, performance enhancing features turned off, etc. In general, you will want to use this setting if your system becomes unstable after you make many changes, to return it to a known good state.
This will not be an optimal setting in the vast majority of cases; you will want to make modifications after you do this, to improve performance . It is very useful for troubleshooting; if your system doesn't work before you run this and then it does work afterwards, you know that an incorrect BIOS setting was likely your problem.
Auto Configuration with Optimal Settings
Select this option to replace most of the current BIOS settings with predefined settings (coded into the BIOS) that are intended to put the system into what the designers consider an optimal state. You can use this when you first start up your system to get it "close" to what you want it to be when you have made all the changes you feel are necessary for maximum performance. Don't expect these optimal settings to truly be optimal however; the designers can't possibly anticipate how you specifically are going to use your system.
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BIOS Settings - Exit Setup
There are generally two ways to exit the BIOS setup program . Most BIOSes have two menu entries that you choose from, to exit either saving your changes, or discarding them. Others exit by hitting the {Esc} key and then ask you if you want to keep changes or discard them.
Save and Exit Setup
Choose this setting to exit the BIOS setup program and save changes to the BIOS CMOS memory . Make sure you select this in order to keep your changes; many times users accidentally forget to do this and then wonder why their system's behavior didn't change even though they modified settings.
Exit Setup Without Saving
Choose this setting to exit the BIOS program discarding all changes made. The BIOS will normally ask for confirmation ("Are you sure?") before exiting. Note that the BIOS program does not keep track of whether or not you actually make changes to any of the settings, the way for example a word processor would, in order to determine if it should warn you. It will warn you every time you tell it to exit without saving.
Hard Disk Drives(HDD)
The hard disk drive in your system is the "data center" of the PC. It is here that all of your programs and data are stored between the occasions that you use the computer. Your hard disk (or disks) are the most important of the various types of permanent storage used in PCs (the others being floppy disks and other storage media such as CD ROMs, tapes, removable drives, etc.) The hard disk differs from the others primarily in three ways: size (usually larger), speed (usually faster) and permanence (usually fixed in the PC and not removable).
Hard disk drives are almost as amazing as microprocessors in terms of the technology they use and how much progress they have made in terms of capacity, speed, and price in the last 20 years. The first PC hard disks had a capacity of 10 megabytes and a cost of over $100 per MB. Modern hard disks have capacities approaching 100 gigabytes and a cost of less than 1 cent per MB! This represents an improvement of 1,000,000% in just under 20 years, or around 67% cumulative improvement per year. At the same time, the speed of the hard disk and its interfaces has increased dramatically as well.
Your hard disk plays a significant role in the following important aspects of your computer system:
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• Performance: The hard disk plays a very important role in overall system performance, probably more than most people recognize (though that is changing now as hard drives get more of the attention they deserve). The speed at which the PC boots up and programs load is directly related to hard disk speed . The hard disk's performance is also critical when multitasking is being used or when processing large amounts of data such as graphics work, editing sound and video, or working with databases.
• Storage Capacity: This is kind of obvious, but a bigger hard disk lets you store more programs and data.
Top view of a 36 GB, 10,000 RPM, IBM SCSI server hard disk, with its top cover removed. Note the height of the drive and the 10 stacked platters. (The IBM Ultrastar 36ZX.)
• Software Support: Newer software needs more space and faster hard disks to load it efficiently. It's easy to remember when 1 GB was a lot of disk space; heck, it's even easy to remember when 100 MB was a lot of disk space! Now a PC with
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even 1 GB is considered by many to be "crippled", since it can barely hold modern (inflated) operating system files and a complement of standard business software.
• Reliability: One way to assess the importance of an item of hardware is to consider how much grief is caused if it fails. By this standard, the hard disk is the most important component by a long shot. As I often say, hardware can be replaced, but data cannot. A good quality hard disk, combined with smart maintenance and backup habits, can help ensure that the nightmare of data loss doesn't become part of your life.
Introduction to File Systems
• File systems. Important topic most crucial data stored in file systems, and file system performance is crucial component of overall system performance. In practice, is maybe the most important.
• What are files? Data that is readily available, but stored on non volatile media. Standard place to store files: on a hard disk or floppy disk. Also, data may be a network away.
• Most systems let you organize files into a tree structure, so have directories and files.
• What is stored in files? Latex source, Nachos source, FrameMaker source, C++ object files, executables, Perl scripts, shell files, databases, PostScript files, etc.
• Meaning of a file depends on the tools that manipulate it. Meaning of a Latex file is different for the Latex executable than for a standard text editor. Executable file format has meaning to OS. Object file format has meaning to linker.
• Some systems support a lot of different file types explicitly. Macintosh, IBM mainframes do this. Knowledge of file types built into OS, and OS handles different kinds of files differently.
• In Unix, meaning of a file is simply a sequence of bytes. How do Unix tools tell file types apart? By looking at contents! For example, how does Unix tell executables apart from shell scripts apart from Perl files when it executes it?
o Shell Scripts start with a #.
o Perl Scripts start with a #!/usr/bin/perl. In general, if file starts with #!tool, Unix shell interprets file using tool.
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o How about executables? Start with Unix executable magic number. Recall Nachos object file format.
o What about PostScript files? Start with something like %!PS Adobe 2.0, which printing utilities recognize.
Single exception: directories and symbolic links are explicitly tagged in Unix.
• What about Macintosh? All files have a type (pict, text) and the name of program that created the file. When double click on the file, it automatically starts the program that created file and loads the file. Have to have utilities that twiddle the file metadata (types and program names).
• What about DOS? Have an ad hoc file typing mechanism built into file naming conventions. So, .com and .exe identify two different kinds of executables. .bat identifies a text batch file. These are enforced by OS (because it is involved with launching executables). Other file extensions are recognized by other programs but not by OS.
• File attributes:
o Name
o Type in Unix, implicit.
o Location where file is stored on disk
o Size
o Protection
o Time, date and user identification.
• All file system information is stored in nonvolatile storage in a way that it can be reconstructed on a system crash. Very important for data security.
• How do programs access files? Several general ways:
o Sequential open it, then read or write from beginning to end.
o Direct specify the starting address of the data.
o Indexed index file by identifier (name, for example), then retrieve record associated by name.
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Files may be accessed more than one way. A payroll file, for example, may be accessed sequentially by paycheck program and indexed by personnel office. Nachos executable files are accessed directly.
• File structure can be optimized for a given access mode.
o For sequential access, can have file just laid out sequentially on disk. What is problem?
o For direct access, can have a disk block table telling where each disk block is. To access indexed data, first traverse disk block table to find right disk block, then go to the block containing data.
o For more sophisticated indexed access, may build an index file. Example: IBM ISAM (Indexed Sequential Access Mode). User selects a key, and system builds a two level index for the key. Uses binary search at each level of index, then linear search within final block. Notice how memory hierarchy considerations drive file implementation.
• Easy to simulate a sequential access file given a direct access file just keep track of current file position. But simulating direct access file with a sequential access file is a lot harder.
• Fundamental design choice: lots of file formats or few file formats? Unix: few (one) file format. VMS: few (three). IBM lots (I don't know just how many).
• Advantage of lots of file formats: user probably has one that fits the bill.
• Disadvantage: OS becomes larger. System becomes harder to use (must choose file format, if get it wrong it is a big problem).
• Directory structure. To organize files, many systems provide a hierarchical file system arrangement. Can have files, and then directories of files. Common arrangement: tree of files. Naming can be absolute, relative, or both.
• There is sometimes a need to share files between different parts of the tree. So, structure becomes a graph. Can get to same file in multiple ways. Unix supports two kinds of links:
o Symbolic Links: directory entry is name of another file. If that file is moved, symbolic link still points to (non existent) file. If another file is copied into that spot, symbolic link all of a sudden points to it.
o Hard Links: sticks with the file. If file is moved, hard link still points to file. To get rid of file, must delete it from all places that have hard links to it.
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Link command (ln) sets these links up.
• Uses for soft links? Can have two people share files. Can also set up source directories, then link compilation directories to source directories. Typically useful file system structuring tool.
• Graph structure introduces complications. First, must be sure not to delete hard linked files until all pointers to them are gone. Standard solution: reference counts. Second, only want to traverse files once even if have multiple references to same file. Standard solution: marking. cp does not handle this well for soft links; tar handles it well.
• What about cyclic graph structures? Problem is that cycles may make reference counts not work can have a section of graph that is disconnected from rest, but all entries have positive reference counts. Only solution: garbage collect. Not done very often because it takes so long.
• Unix prevents users from making hard links create cycles by only allowing hard links to point to files, not directories. But, with .. still have some cycles in structure.
• Memory mapped files. Standard view of system: have data stored in address space of a process, but data goes away when process dies. If want to preserve data, must write it to disk, then read it back in again when need it.
• Writing IO routines to dump data to disk and back again is a real hassle. What is worse, if programs share data using files, must maintain consistency between file and data read in via some other mechanism.
• Solution: memory mapped files. Can map part of file into process's address space and read and write the file like a normal piece of memory. Sort of like memory mapped IO, generalized to user level. So, processes can share persistent data directly with no hassles. Programs can dump data structures to disk without having to write routines to linearize, output and read in data structures.
• Used for stuff like snapshot files in interactive systems.
• In Unix, the system call that sets this up is the mmap system call. How is sharing set up for processes on the same machine? What about processes on different machines?
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• Next issue: protection. Why is protection necessary? Because people want to share files, but not share all aspects of all files. Want protection on individual file and operation basis.
o Professor wants students to read but not write assignments.
o Professor wants to keep exam in same directory as assignments, but students should not be able to read exam.
o Can execute but not write commands like cp, cat, etc.
For convenience, want to create coarser grain concepts.
o All people in research group should be able to read and write source files. Others should not be able to access them.
o Everybody should be able to read files in a given directory.
• Conceptually, have operations (open, read, write, execute), resources (files) and principals (users or processes). Can describe desired protection using access matrix. Have list of principals across top and resources on the side. Each entry of matrix lists operations that the principal can perform on the resource.
• Two standard mechanisms for access control: access lists and capabilities.
o Access lists: for each resource (like a file), give a list of principals allowed to access that resource and the access they are allowed to perform. So, each row of access matrix is an access list.
o Capabilities: for each resource and access operation, give out capabilities that give the holder the right to perform the operation on that resource. Capabilities must be unforgivable. Each column of access matrix is a capability list.
Instead of organizing access lists on a principal by principal basis, can organize on a group basis.
• Who controls access lists and capabilities? Done under OS control. Will talk more about security later.
• What is the Unix security model? Have three operations read, write and execute. Each file has an owner and a group. Protections are given for each operation on basis of everybody, group and owner. Like everything else in Unix, is a fairly simple and primitive protection strategy.
• Unix file listing:
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• 4 drwxr xr 2 martin faculty 2048 May 15 21:03 ./
• 2 drwxr xr x 7 martin faculty 512 May 3 17:46 ../
• 2 rw r 1 martin faculty 213 Apr 19 22:27 a0.aux
• 8 rw r 1 martin faculty 3488 Apr 19 22:27 a0.dvi
• 4 rw r 1 martin faculty 1218 Apr 19 22:27 a0.log
• 72 rw r r 1 martin faculty 36617 Apr 19 22:27 a0.ps
• 6 rwxr xr x 1 martin faculty 2599 Apr 5 18:07 a0.tex*
• How are files implemented on a standard hard disk based system? It is up to OS to implement it. Why must OS do this? Protection.
• What does a disk look like? It is a stack of platters. Each platter may have two surfaces (one per side). There is one disk head per surface. The surfaces revolve beneath the heads, with the heads riding on a cushion of air. The heads move back and forth between the platters as a unit. The area beneath a stationary head is a track. The set of tracks that can be accessed without moving the heads is a cylinder. Each track is broken up into sectors. A sector is the unit of disk transfer.
• To read a given sector we first move the heads to that sector's cylinder (seek time), then wait for the sector to rotate under the head (latency time), then copy data off of disk into memory (transfer time).
• Typical hard disk statistics: (Sequel 5400 from August 1993, 5.25 inch 4.0Gbyte).
o Platters: 13
o Read/Write heads: 26
o Tracks/Surface: 3,058
o Track Capacity (bytes): 40,448 60,928
o Bytes/Sector: 512 520
o Sectors/Track: 79 119
o Media Transfer Rate (MB/s): 3.6 5.5
o Track to track Seek: 1.3 ms
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o Max Seek: 25 ms
o Average Seek: 12 ms
o Rotational Speed: 5,400 rpm
o Average Latency: 5.6 ms
• How does this compare to timings for a standard workstation? DEC Station 5000 is a standard workstation available in 1993. Had a 33 MHz MIPS R3000, 60 ns memory. How many instructions can execute in 30 ms (about time for average seek plus average latency)? 33 * 30 * 1000 = 990,000. Plus, many operations require multiple disk accesses.
• What does disk look like to OS? Is just a sequence of sectors. All sectors in a track are in sequence; all tracks in a cylinder are in sequence. Adjacent cylinders are in sequence. OS may logically link several disk sectors together to increase effective disk block size.
• How does OS access disk? There is a piece of hardware on the disk called a disk controller. OS issues instructions to disk controller. Can either use IO instructions or memory mapped IO operations.
• In effect, disk is just a big array of fixed size chunks. Job of the OS is to implement file system abstractions on top of these chunks.
Different types file system
When there is a valid need to properly store and to organize your business computer files your company should not be constrained with using only a single type of filing system. In effect there is more than one type of file system that can be used for your purpose. To actually be more precise there are a total of four different styles or types of systems at your command. These systems are your disk file systems; the network file systems as well as the various special purposes file systems. We will briefly cover each of these systems in turn.
The disk file system is perhaps the most common means employed for storing and maintaining both personal and business related files. These are easy to use and can be used at your home or at your place of employment. The maintenance and the storage of these files are facilitated only by the data storage devices themselves such as by the use of the common disk drive. The disk file system used by an organization can use either the FAT, NTFS, HFS or a few of the lesser known methods which we will not discuss here. It is better to keep to the major types of systems in order to facilitate compatibility.
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Another quickly growing type of file system is the Flash file system. This is the choice of system if your intention is to store your data on the portable flash memory devices. The popularity of these storage media devices has grown alongside the popular mobile devices and the closely related flash memories. Though it is a common misunderstanding to employ the use of the usual disk file system on the flash device it quickly becomes apparent that by doing so will simply not bring out the best results of this system.
We next have the network file system which is quickly gaining in popularity not only in the business environment but in private homes as well. This system makes use of what is known as remote file access protocol. This protocol provides users the necessary access for files which are stored on a common server.
The last type of file system that we will briefly discus is the special purpose file system. Simply put, any file system which is not a network or a disk file system would fall under this new category of file system. Generally these types of systems are in house designed specifically for a particular purpose by the computer department of major corporations. This type of data bases and file structures do not adapt very well from one field of use to another. As an example you would not want to try and use a specially designed meat production file system for use with an auto industry company complex.
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. 4 Unit – 2 Input and output devices The computer will be of no use unless it is able to communicate with the outside world. Input/output devices are required for users to communicate with the computer. In simple terms, input devices bring information INTO the computer and output devices bring information OUT of a computer system. These input/output devices are also known as peripherals since they surround the CPU and memory of a computer system. Some commonly used Input/Output devices are listed in table below.
Input Devices Output Devices Keyboard Monitor Mouse LCD Joystick Printer Scanner Plotter Light Pen Touch Screen Input devices Keyboard It is a text base input device that allows the user to input alphabets, numbers and other characters. It consists of a set of keys mounted on a board.
Alphanumeric Keypad/ Function Keys Special function Keys Cursor Movement Keys
Numeric Keypad
Figure 1.7 : Qwerty Keyboard Layout Alphanumeric Keypad It consists of keys for English alphabets, 0 to 9 numbers, and special characters like + − / * ( ) etc.
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Function Keys There are twelve function keys labeled F1, F2, F3, , F12. The functions assigned to these keys differ from one software package to another. These keys are also user programmable keys. Special-function Keys These keys have special functions assigned to them and can be used only for those specific purposes. Functions of some of the important keys are defined below. Enter It is similar to the ‘return’ key of the typewriter and is used to execute a command or program. Spacebar It is used to enter a space at the current cursor location. Backspace This key is used to move the cursor one position to the left and also delete the character in that position. Delete It is used to delete the character at the cursor position. Insert Insert key is used to toggle between insert and overwrite mode during data entry. Shift This key is used to type capital letters when pressed along with an alphabet key. Also used to type the special characters located on the upper side of a key that has two characters defined on the same key. Caps Lock Cap Lock is used to toggle between the capital lock feature. When ‘on’, it locks the alphanumeric keypad for capital letters input only. Tab Tab is used to move the cursor to the next tab position defined in the document. Also, it is used to insert indentation into a document. Ctrl Control key is used in conjunction with other keys to provide additional functionality on the keyboard.
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Alt Also like the control key, Alt key is always used in combination with other keys to perform specific tasks. Esc This key is usually used to negate a command. Also used to cancel or abort executing programs. Numeric Keypad Numeric keypad is located on the right side of the keyboard and consists of keys having numbers (0 to 9) and mathematical operators (+ − * /) defined on them. This keypad is provided to support quick entry for numeric data. Cursor Movement Keys These are arrow keys and are used to move the cursor in the direction indicated by the arrow (up, down, left, right). Mouse The mouse is a small device used to point to a particular place on the screen and select in order to perform one or more actions. It can be used to select menu commands, size windows, start programs etc. The most conventional kind of mouse has two buttons on top: the left one being used most frequently. Mouse Actions Left Click : Used to select an item. Double Click : Used to start a program or open a file. Right Click : Usually used to display a set of commands. Drag and Drop : It allows you to select and move an item from one location to another. To achieve this place the cursor over an item on the screen, click the left mouse button and while holding the button down move the cursor to where you want to place the item, and then release it. Joystick The joystick is a vertical stick which moves the graphic cursor in a direction the stick is moved. It typically has a button on top that is used to select the option pointed by the cursor. Joystick is used as an input device primarily used with video games, training simulators and controlling robots.
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Figure 1.8 : Mouse Figure 1.9 : Joystick Scanner Scanner is an input device used for direct data entry from the source document into the computer system. It converts the document image into digital form so that it can be fed into the computer. Capturing information like this reduces the possibility of errors typically experienced during large data entry.
Figure 1.10 : A Flat -bed Scanner Hand held scanners are commonly seen in big stores to scan codes and price in formation for each of the items. MIC
A microphone (colloquially called a mic or mike ; both pronounced /ˈma ɪk/ [1] ) is an acoustic to electric transducer or sensor that converts sound into an electrical signal . Microphones are used in many applications such as telephones, tape recorders , karaoke systems, hearing aids , motion picture production, live and recorded audio engineering, FRS radios, megaphones , in radio and television broadcasting and in computers for recording voice, speech recognition, VoIP, and for non acoustic purposes such as ultrasonic checking or knock sensors. Most microphones today use electromagnetic induction (dynamic microphone), capacitance change (condenser microphon e), piezoelectric generation, or light modulation to produce an electrical voltage signal from mechanical vibration. Light Pen It is a pen shaped device used to select objects on a display screen. It is quite like the mouse (in its functionality) but uses a light pen to move the pointer and select any object on the screen by pointing to the object.
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Users of Computer Aided Design (CAD) applications commonly use the light pens to directly draw on screen. Touch Screen It allows the user to operate/make selections by simply touching the display screen. Common examples of touch screen include information kiosks, and bank ATMs.
Output Devices Monitor - A monitor is the screen on which words, numbers, and graphics can be seem. The monitor is the most common output device.
Compact Disk Some compact disks can be used to put information on. This is called burning information to a CD.
NOTE: A CD can also be an input device.
Printer - A printer prints whatever is on the monitor onto paper. Printers can print words, numbers, or pictures.
Speaker - A speaker gives you sound output from your computer. Some speakers are built into the computer and some are separate.
Disk Drives - A disk drive is used to record information from the computer onto a floppy disk or CD.
Floppy Disk - A floppy disk is used to record information on. The information is stored on the floppy disk and can be used later or used on another computer
Headphones - Headphones give sound output from the computer. They are similar to speakers, except they are worn on the ears so only one person can hear the output at a time.
Monitor Monitor is an output device that resembles the television screen and uses a Cathode Ray Tube (CRT) to display information. The monitor is associated with a keyboard for manual input of characters and displays the information as it is keyed in. It also displays the program or application output. Like the television, monitors are also available in different sizes.
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Figure 1.11 : Monitor
Monitor and Types
There are three main types of monitors: the CRT, or Cathode Ray Tube monitor, the LCD Flat Panel monitor, and the TFT LCD monitor.
Each has their own advantages. To learn more about the different types of monitors, just click on any of the links:
CRT (Cathode Ray Tube) Monitor
This is the most inexpensive monitor in the market today. It sports quite a large case, which includes the flat/funnel tubes that displays the images on the screen.
Pixels, made up of phosphors, are the tiny components that make up the image shown onscreen. These pixels are struck by electrons, which make the pixels glow and eventually form the desired image on the screen.
LCD Flat Panel Monitor
Liquid Crystal Display (LCD) monitors were first developed for use with laptop computers. Also known as flat screen monitors, they are becoming more and more common these days. When initially introduced in the market, these flat screens cost quite a fortune. But with its proliferation, prices are continuing to drop.
LCD technology makes use of a liquid crystal solution that are present in two panes of polarized and partitioned glasses. By adjusting the amount of light that passes through these panels through an electric voltage, images are created on the screen. This technology also reduces blurring and color smudging during motion pictures, which makes this type of monitor appropriate for gamers or film enthusiasts.
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These compact screens are perfect for those who don’t have much space to spare on their office desks or at home. Moreover, due to its technology, the display is also far superior than the CRT monitor’s.
A downside to this type is that, aside from being more expensive, it costs to have some add ons attached to it, such as SVGA, or Super Video Graphics Array technology for improved onscreen display. A DVI input, or Digital Visual Interface, is also recommended for this type of monitor.
TFT-LCD Monitor
A Thin Film Transistor (TFT) – LCD monitor is now being more widely used with LCD monitors, because of of its high level of resolution and sharpness. The only difference is a thin film transistor that is applied to the screen, which results in better control of pixels.
This type of monitor is recommended for those who play animated, colorful, and high resolution games, as well as graphic artists who may need to check out different fonts on the computer screen. Printer
Printers are used to produce paper (commonly known as hardcopy) output. Based on the technology used, they can be classified as Impact or Non-impact printers. Impact printers use the typewriting printing mechanism wherein a hammer strikes the paper through a ribbon in order to produce output. Dot matrix and Character printers fall under this category. Non-impact printers do not touch the paper while printing. They use chemical, heat or electrical signals to etch the symbols on paper. Inkjet, Deskjet, Laser, Thermal printers fall under this category of printers. When we talk about printers we refer to two basic qualities associated with printers: resolution, and speed. Print resolution is measured in terms of number of dots per inch (dpi). Print speed is measured in terms of number of characters printed in a unit of time and is represented as characters per second (cps), lines per minute (lpm), or pages per minute (ppm). Printers and its types Printers are hardware devices which help to take print out of documents from the computer and there are a lot of advantages in using Printers. Printers are efficient devices connected to a computer. They allow the users to print text and images on paper. There are wide varieties of printers which suit all kinds of people. Printers are
67 | P a g e classified based on the printing materials they use and the way they obtain data from the computer. Computer speakers
Computer speakers , or multimedia speakers , are speakers external to a computer, that disable the lower fidelity built in speaker. They often have a low power internal amplifier. The standard audio connection is a 3.5 mm (approximately 1/8 inch) stereo jack plug often color coded lime green (following the PC 99 standard) for computer sound cards. A plug and socket for a two wire (signal and ground) coaxial cable that is widely used to connect analog audio and video components. Rows of RCA sockets are found on the backs of stereo amplifier and numerous A/V products. The prong is 1/8" thick by 5/16" long. A few use an RCA connector for input. There are also USB speakers which are powered from the 5 volts at 500 milliamps provided by the USB port, allowing about 2.5 watts of output power. Computer speakers range widely in quality and in price. The computer speakers typically packaged with computer systems are small, plastic, and have mediocre sound quality. Some computer speakers have equalization features such as bass and treble controls. The internal amplifiers require an external power source, usually an AC adapter. More sophisticated computer speakers can have a subwoofer unit, to enhance bass output, and these units usually include the power amplifiers both for the bass speaker, and the small satellite speakers. Some computer displays have rather basic speakers built in. Laptops come with integrated speakers. Restricted space available in laptops means these speakers usually produce low quality sound. For some users, a lead connecting computer sound output to an existing stereo system is practical. This normally yields much better results than small low cost computer speakers. Computer speakers can also serve as an economy amplifier for MP3 player use for those who wish to not use headphones, although some models of computer speakers have headphone jacks of their own. Types of printer
Inkjet printers - These printers are commonly used in households and small offices. They are cheap to buy and maintain. This printer works with a cartridge, usually a black cartridge. But other individual color cartridges can also be used with it to produce pictures and colored fonts. These printers come in various styles from attractive glossy ones to professional ones.
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Laser printers – The laser printers uses the toner cartridge and it is fitted into the printer. The print gener ated is of good quality and works fast. These printers print higher volume than the ink jet at the given time. Because of its performance they tend to be more costly and it is best suited for offices and commercial establishments.
‘All in 1’ printers - The se types of printers are for multi tasking. They consist of the laser cartridge, a copier, a scanner and sometimes even fax facility in one single package. With these multiple functionality they are becoming more popular. This really is suited for small of fices or a home office since they tender the printing, scanning and faxing in one single unit. But in big organizations a dedicated machine for each should do better since the quality of print may not be astonishing.
Photo or Snapshot printers - This devic e prints your pictures and photos with fine quality. This is not possible with other types of printers. An inkjet printer can print photos but it cannot meet the outcome given by this kind of printer. These printers have started coming in advanced versions where you can print photos directly from your camera and that does not require your computer to be turned on.
It is a hard task to buy a printer because of the variety in sizes, design and types of printers. Be it your personal use or for company use, you can always find a printing device available in the market which suits your taste of printing needs. Being careful while choosing is more important than buying the printers. Plotter Plotters are used to print graphical output on paper. It interprets com puter commands and makes line drawings on paper using multicoloured automated pens. It is capable of producing graphs, drawings, charts, maps etc.
An Inkjet Printer Flatbed Plotter Computer Aided Engineering (CAE) applications like CAD (Computer Aided Design) and CAM (Computer Aided Manufacturing) are typical usage areas for plotters.
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Unit – 3
Memory
The main memory in the computer system is referred to as RAM (Random Access Memory). It is fast access memory and is used to store data and instructions during computer operations. The main feature of RAM is that it can be read from and written onto any location and can be accessed randomly (hence the name RAM). The contents of RAM are available only as long as the computer is on and are lost once it is switched off. It is, therefore, also called ‘volatile’ memory. Secondary storage can be used to store data and instructions permanently. ROM or Read Only Memory holds data or instructions permanently and as the name suggest, can only be read from but cannot be changed by the users. It is non volatile in nature, which means that contents of ROM are not lost even if the power is switched off. It, therefore, usually contains instructions that are required to get the computer started once it is powered on. The contents of ROM are built into it at the time of manufacturing itself. Random Access Memory (RAM): The primary storage is referred to as random access memory (RAM) because it is possible to randomly select and use any location of the memory directly store and retrieve data. It takes same time to any address of the memory as the first address. It is also called read/write memory. The storage of data and instructions inside the primary storage is temporary. It disappears from RAM as soon as the power to the computer is switched off. The memories, which lose their content on failure of power supply, are known as volatile memories .So now we can say that RAM is volatile memory. Read Only Memory (ROM):
There is another memory in computer, which is called Read Only Memory (ROM). Again it is the ICs inside the PC that form the ROM. The storage of program and data in the ROM is permanent. The ROM stores some standard processing programs supplied by the manufacturers to operate the personal computer. The ROM can only be read by the CPU but it cannot be changed. The basic input/output program is stored in the ROM that examines and initializes various equipment attached to the PC when the switch is made ON. The memories, which do not lose their content on failure of power supply, are known as non volatile memories. ROM is non volatile memory.
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Primary Memory
Primary memory is the memory that can be directly accessed by the CPU which constantly interacts with it, retrieves data stored therein, goes through instructions and execute them as per the requirement. All the information, data and application are loaded there in uniform manner. Earlier William tubes, delay lines or rotating magnetic drums were used as primary storage which were later replaced by magnetic core memory. Solid state silicon chip technology revolutionized the electronic memory and paved the way for Random Access Memory (RAM). RAM is volatile (temporary) but fast form of memory.
Apart from the main large capacity Random Access Memory (RAM), there are two sub layers of the primary memory.
Processor registers within the processor, which are one of the fastest forms of data storage, contain a word of data (usually 32 or 64 bits). The CPU instructs and helps the Arithmetic and logic unit to perform a number of calculations on this data.
Processor cache, which is meant for enhancing the performance of the computer, links the fast registers to the slower main memory. Cache memory loads the duplicated information that is used most actively. It is much faster than the main memory but relatively can store limited data. It is also much slower but much larger than the processor registers. Cache setup is further split into different levels with smallest and fastest primary cache and relatively larger but slower secondary cache.
SECONDARY STORAGE
You are now clear that the operating speed of primary memory or main memory should be as fast as possible to cope up with the CPU speed. These high speed storage devices are very expensive and hence the cost per bit of storage is also very high. Again the storage capacity of the main memory is also very limited. Often it is necessary to store hundreds of millions of bytes of data for the CPU to process. Therefore additional memory is required in all the computer systems. This memory is called auxiliary memory or secondary storage.
In this type of memory the cost per bit of storage is low. However, the operating speed is slower than that of the primary storage. Huge volume of data are stored here on permanent basis and transferred to the primary storage as and when required. Most widely used secondary storage devices are magnetic tapes and magnetic disk.
1.Magnetic Tape:
Magnetic tapes are used for large computers like mainframe computers where large volume of data is stored for a longer time. In PC also you can use tapes in the form of
71 | P a g e cassettes. The cost of storing data in tapes is inexpensive. Tapes consist of magnetic materials that store data permanently. It can be 12.5 mm to 25 mm wide plastic film type and 500 meter to 1200 meter long which is coated with magnetic material. The deck is connected to the central processor and information is fed into or read from the tape through the processor. It similar to cassette tape recorder.
Advantages of Magnetic Tape:
Compact:
A 10 inch diameter reel of tape is 2400 feet long and is able to hold 800, 1600 or 6250 characters in each inch of its length. The maximum capacity of such tape is 180 million characters. Thus data are stored much more compactly on tape.
Economical:
The cost of storing characters is very less as compared to other storage devices.
Fast:
Copying of data is easier and fast.
Long term Storage and Re-usability:
Magnetic tapes can be used for long term storage and a tape can be used repeatedly with out loss of data.
2.Magnetic Disk:
You might have seen the gramophone record, which is circular like a disk and coated with magnetic material. Magnetic disks used in computer are made on the same principle. It rotates with very high speed inside the computer drive. Data is stored on both the surface of the disk. Magnetic disks are most popular for direct access storage device. Each disk consists of a number of invisible concentric circles called tracks. Information is recorded on tracks of a disk surface in the form of tiny magnetic spots. The presence of a magnetic spot represents one bit and its absence represents zero bit. The information stored in a disk can be read many times without affecting the stored data. So the reading operation is non destructive. But if you want to write a new data, then the existing data is erased from the disk and new data is recorded.
Floppy Disk:
It is similar to magnetic disk discussed above. They are 5.25 inch or 3.5 inch in diameter. They come in single or double density and recorded on one or both surface of the diskette. The capacity of a 5.25 inch floppy is 1.2 mega bytes whereas for 3.5 inch
72 | P a g e floppy it is 1.44 mega bytes. It is cheaper than any other storage devices and is portable. The floppy is a low cost device particularly suitable for personal computer system.
Optical Disk:
With every new application and software there is greater demand for memory capacity. It is the necessity to store large volume of data that has led to the development of optical disk storage medium. Optical disks can be divided into the following categories:
1.Compact Disk/ Read Only Memory (CD-ROM):
CD ROM disks are made of reflective metals. CD ROM is written during the process of manufacturing by high power laser beam. Here the storage density is very high, storage cost is very low and access time is relatively fast. Each disk is approximately 4 1/2 inches in diameter and can hold over 600 MB of data. As the CD ROM can be read only we cannot write or make changes into the data contained in it.
2.Write Once, Read Many (WORM):
The inconvenience that we can not write any thing in to a CD ROM is avoided in WORM. A WORM allows the user to write data permanently on to the disk. Once the data is written it can never be erased without physically damaging the disk. Here data can be recorded from keyboard, video scanner, OCR equipment and other devices. The advantage of WORM is that it can store vast amount of data amounting to gigabytes (109 bytes). Any document in a WORM can be accessed very fast, say less than 30 seconds.
3.Erasable Optical Disk:
These are optical disks where data can be written, erased and re written. This also applies a laser beam to write and re write the data. These disks may be used as alternatives to traditional disks. Erasable optical disks are based on a technology known as magnetic optical (MO). To write a data bit on to the erasable optical disk the MO drive's laser beam heats a tiny, precisely defined point on the disk's surface and magnetises it.
Memory Packages
SIP
There are many applications of the Internet that require the creation and management of a session, where a session is considered an exchange of data between an associations of participants. The implementation of these applications is complicated by
73 | P a g e the practices of participants: users may move between endpoints, they may be addressable by multiple names, and they may communicate in several different media sometimes simultaneously. Numerous protocols have been authored that carry various forms of real time multimedia session data such as voice, video, or text messages. The Session Initiation Protocol (SIP) works in concert with these protocols by enabling Internet endpoints (called user agents) to discover one another and to agree on a characterization of a session they would like to share. For locating prospective session participants, and for other functions, SIP enables the creation of an infrastructure of network hosts (called proxy servers) to which user agents can send registrations, invitations to sessions, and other requests. SIP is an agile, general purpose tool for creating, modifying, and terminating sessions that works independently of underlying transport protocols and without dependency on the type of session that is being established. Computer Memory Types and Memory Technology
Memory Types
In order to enable computers to work faster, there are several types of memory available today. Within a single computer there is no longer just one type of memory. Because the types of memory relate to speed, it is important to understand the differences when comparing the components of a computer.
SIMM (Single In-line Memory Modules)
SIMMs are used to store a single row of DRAM, EDO or BEDO chips where the module is soldered onto a PCB. One SIMM can contain several chips. When you add more memory to a computer, most likely you are adding a SIMM.
The first SIMMs transferred 8 bits of data at a time and contained 30 pins. When CPU's began to read 32 bit chunks, a wider SIMM was developed and contained 72 pins.
72 pin SIMMS are 3/4" longer than 30 pin SIMMs and have a notch in the lower middle of the PCB. 72 pin SIMMs install at a slight angle.
DIMM (Dual In-line Memory Modules)
DIMMs allow the ability to have two rows of DRAM, EDO or BEDO chips. They are able to contain twice as much memory on the same size circuit board. DIMMs contain 168 pins and transfer data in 64 bit chunks.
DIMMs install straight up and down and have two notches on the bottom of the PCB.
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SODIMM (Small Outline DIMM)
SO DIMMs are commonly used in notebooks and are smaller than normal DIMMs. There are two types of SO DIMMs. Either 72 pins and a transfer rate of 32 bits or 144 pins with a transfer rate of 64 bits.
RDRAM - RIMM
Rambus, Inc, in conjunction with Intel has created new technology, Direct RDRAM, to increase the access speed for memory. RIMMs appeared on motherboards sometime during 1999. The in line memory modules are called RIMMs. They have 184 pins and provide 1.6 GB per second of peak bandwidth in 16 bit chunks. As chip speed gets faster, so does the access to memory and the amount of heat produced. An aluminum sheath, called a heat spreader, covers the module to protect the chips from overheating.
SO RIMM
Similar in appearance to a SODIMM and uses Rambus technology. Technology
DRAM (Dynamic Random Access Memory)
One of the most common types of computer memory (RAM). It can only hold data for a short period of time and must be refreshed periodically. DRAMs are measured by storage capability and access time.
Storage is rated in megabytes (8 MB, 16 MB, etc).
Access time is rated in nanoseconds (60ns, 70ns, 80ns, etc) and represents the amount of time to save or return information. With a 60ns DRAM, it would require 60 billionths of a second to save or return information. The lower the nanospeed, the faster the memory operates.
DRAM chips require two CPU wait states for each execution.
Can only execute either a read or write operation at one time.
FPM (Fast Page Mode)
At one time, this was the most common and was often just referred to as DRAM. It offered faster access to data located within the same row.
EDO (Extended Data Out)
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Newer than DRAM (1995) and requires only one CPU wait state. You can gain a 10 to 15% improvement in performance with EDO memory.
BEDO (Burst Extended Data Out )
A step up from the EDO chips. It requires zero wait states and provides at least another 13 percent increase in performance.
SDRAM (Static RAM)SDRAM, DDR, RAMBUS
Introduced in late 1996, retains memory and does not require refreshing. It synchronizes itself with the timing of the CPU. It also takes advantage of interleaving and burst mode functions. SDRAM is faster and more expensive than DRAM. It comes in speeds of 66, 100, 133, 200, and 266MHz.
DDR SDRAM (Double Data Rate Synchronous DRAM)
Allows transactions on both the rising and falling edges of the clock cycle. It has a bus clock speed of 100MHz and will yield an effective data transfer rate of 200MHz.
Direct Rambus
Extraordinarily fast. By using doubled clocked provides a transfer rate up to 1.6GBs yielding a 800MHz speed over a narrow 16 bit bus.
Cache RAM
This is where SRAM is used for storing information required by the CPU. It is in kilobyte sizes of 128KB, 256KB, etc. Other Memory Types
VRAM (Video RAM)
VRAM is a video version of FPM and is most often used in video accelerator cards. Because it has two ports, It provides the extra benefit over DRAM of being able to execute simultaneous read/write operations at the same time. One channel is used to refresh the screen and the other manages image changes. VRAM tends to be more expensive.
Flash Memory
This is a solid state, nonvolatile, rewritable memory that functions like RAM and a hard disk combined. If power is lost, all data remains in memory. Because of its high speed, durability, and low voltage requirements, it is ideal for digital cameras, cell phones, printers, handheld computers, pagers and audio recorders.
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Shadow RAM
When your computer starts up (boots), minimal instructions for performing the startup procedures and video controls are stored in ROM (Read Only Memory) in what is commonly called BIOS. ROM executes slowly. Shadow RAM allows for the capability of moving selected parts of the BIOS code from ROM to the faster RAM memory
Cache Memory
The cache memory is very important to the PC system and its speed. Cache sits on newer processor as L1 (level 1) memory and as L2 memory. This allows kind of a buffer for the CPU. The CPU (Central Processing Unit ) is faster than the rest of the system in most cases and needs a place to store information that can be accessed fast, this is where L1 and L2 come in. The cache minimizes the number of outgoing transactions from the CPU, it sends and receives information from the system memory and passes it to the CPU so the CPU can do more of its work internally thus speeding overall pc performance.
L1 Cache , you might have hear of L2 cache when looking at specs of a computer. The L1 cache is a little more hush hush. This cache site on the CPU an allows a buffer for the rest of the system to keep up with it. The same goes with L2 cache but act more for information heading out of the CPU rather than in it.
Workings
The cache itself is made up of extremely fast silicon memory, and is called SRAM (Static RAM). This is a super fast RAM and isn't cheap, the L1 cache has a much lower latency than L2 cache that is why most L1 cache's have 32 64kb as the cost is much higher, and L2 have 512kb to 2MB. Something to keep in mind is that a high cache size doesn't mean better.
The L2 chips, themselves that are split up into two sections. These sections are main data, tag data cache chips. The tag RAM chip determines where the needed data is on the main data chip. Types Of Cache
There are three types of cache out there.
Asynchronous SRAM, this RAM has speeds of 12, 15, 20 nanoseconds. The RAM is called asynchronous because the processor has provide a address for each cache access then in turn has to wait. This is a older type cache and is found on 386 and 486 machines.
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Synchronous Burst SRAM, This is like the name implies and allows for the RAM to work in step with the system clock. It also free ups the problems with the CPU. In other words less waiting.
Pipeline Burst SRAM, this type is much like the Synchronous and is far cheaper. Found on current Pentium systems.
Where Is It?
The L1 and L2 cache are now found on the CPU. Old systems used to have the L2 cache on the actual motherboard .
CACHE
A cache is a form of SRAM that is easily and faster to access by a processor. The cache is usually labelled according to its distance from the processor. A level 1 cache is a cache built on the same platform with the processor, while a Level 2 cache is not built on the same platform with the processor. It is usually measured in bytes. A byte is the equivalent of eight bits and a bit is any of the 0’s and 1’s, which make up the binary digits. The standard measure of the Level 1 cache is Kilobytes (KB) meaning thousand of bytes or multiples of 8,000 bits.
The cache memory can be referred as associative memory or associative registers, content addressable memory, or a translation look aside buffer (John O'Gorman).
It is pronounced cash, a special high speed storage mechanism. It can be either a reserved section of main memory or an independent high speed storage device.
Two types of caching are commonly used in personal computers: MEMORY caching and DISK caching. We are interested in memory caching but disk caching will be discussed briefly. MEMORY CACHE:
A memory cache, sometimes called a cache store or RAM cache, is a portion of memory made of high speed static RAM (SRAM) instead of the slower and cheaper
78 | P a g e dynamic RAM (DRAM) used for main memory. Cache memory dramatically raises the performance of a computer system at relatively little cost. Memory caching is effective because most programs access the same data or instructions over and over. By keeping as much of this information as possible in SRAM, the computer avoids accessing the slower DRAM.
Cache memory is hidden from the programmer and appears as part of the system's memory space. Some memory caches are built into the architecture of
Microprocessors. For example, the Intel 80486 microprocessor contains an 8K memory cache, and the Pentium has a 16K cache. 64K bytes of a cache memory in a system with 4M bytes of DRAM, with this, it expects the processor to make over 95% of its accesses to the cache rather than the slower DRAM.
Such internal caches are often called Level 1 (L1) caches. Most modern PCs also come with external cache memory, called Level 2 (L2) caches. These caches sit between the CPU and the DRAM. Like L1 caches, L2 caches are composed of SRAM but they are much larger (CACHE Webopedia.com).
There exist different levels and types of cache Disk Cache :
• A disk cache is a portion of a system memory used to cache reads and writes to the hard disk. It may be referred to as the most important type of cache on the
• PC, because of the greatest differential speed between the layers, that is the system RAM and the hard disk. Disk caching works under the same principle as
• Memory caching, but instead of using high speed SRAM, a disk cache uses conventional main memory. The most recently accessed data from the disk is stored in a memory buffer. When a program needs to access data from the disk, it first checks the disk cache to see if the data is there. Disk caching can dramatically improve the performance of applications, because accessing a byte on a hard disk.
• While the system RAM is slightly slower than the level 1 or level 2 caches, the hard disk is much slower than the system RAM. Disk caches are usually implemented using software such as DOS's Smart Drive. When data is found in the cache, it is called a cache hit, and the effectiveness of a cache is judged by its hit rate. Many cache systems use a technique known as smart caching, in which the system can recognise certain types of frequently used data. The strategies for determining which information should be kept in the cache constitute some of the more interesting caching problems in computer.
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Peripheral Cache :
• Other devices can be cached using the system RAM. CD ROMs are the most common device cache other than hard disks, particularly due to their very slow initial access time. In certain cases, CD ROM drives are cached to the hard disk, since the hard disk is still faster than the CD ROM drive.
• Finally, we have mentioned and explained the different types of caches. The level 1 and level 2 caches memory are mainly devoted to caching while system RAM is used partially for caching
FLASH memory and EEPROM are non volatile memory solutions that are widely used in embedded systems applications. They are available both on chip and as external, stand alone memory. The Keil 8051 , 251 , and C16x/ST10 development tools allow you to write software for all FLASH based chips and microcontrollers that are available. Uses for FLASH Memory
• Using FLASH Memory for Program Code Program code may be stored in FLASH using any of a number of schemes . Embedded applications that must be updated benefit from FLASH memory. These systems can easily be programmed externally by device programmers and many can be re programmed in system.
• Using FLASH Memory for Data Storage FLASH can also be used for configuration data and mass storage. These systems are typically updated on the fly in system. Since FLASH is non volatile (unless it's broken) these systems can restore configuration parameters after a power failure or reset. Accessing FLASH Memory
In either case, your application must include code that allows you to read (or execute) and write the FLASH memory.
Reading FLASH memory works just like reading any other type of memory. The only difference with FLASH is that you may have a special format for the data it holds. This can best be represented by a C struct.
Executing from FLASH memory also works just like executing from any other type of memory. Your FLASH device (and the code it contains) start at a specific address. When you create a program that is loaded into FLASH for execution you may be
80 | P a g e required to relocate that code when programming the device (for example, upload to XDATA/RAM then write into FLASH).
Writing FLASH memory involves some real work. You must have routines that erase the FLASH and write bytes or blocks. Because of the number of different devices, these routines must be customized for each different device.
Secondary storage device
Alternatively referred to as external memory and auxiliary storage , secondary storage is a storage medium that holds information until it is deleted or overwritten regardless if the computer has power. For example, a floppy disk drive and hard disk drive are both good examples of secondary storage devices. As can be seen by the below picture there are three different storage on a computer, although primary storage is accessed much faster than secondary storage because of the price and size limitations secondary storage is used with today's computers to store all your programs and your personal data.
Finally, although off line storage could be considered secondary storage, we've separated these into their own category because this media can be easily removed from the computer and stored elsewhere FDD
A Floppy Disk Drive , or FDD for short, is a computer disk drive that enables a user to easily save data to removable diskettes. Although 8" disk drives made available in 1971 were the first real disk drives, the first widely used an floppy disk drives were the 5 1/4" floppy disk drives, which were later replaced with 3 1/2" floppy disk drives. However, today because of the limited capacity and reliability of floppy diskettes many computers
81 | P a g e no longer come equipped with floppy disk drives and are being replaced with CD R and other writable disc drives and flash drives .
Above is an example of each of the different floppy drives. As can be seen the size of the floppy drives and their disks have greatly decreased over time
Hard drive
The computer's main storage media device used to permanently store all data on the computer. Also referred to as a hard disk drive or abbreviated as HD or HDD , the hard drive was first introduced on September 13, 1956 and consists of one or more hard disk platters inside of air sealed casing. Most hard drives are permanently stored in an internal drive bay at the front of the computer and are connected with either ATA , SCSI , or a SATA cable and power cable. Below is an illustration of the inside of a hard disk drive.
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As can be seen in the above picture of the desktop hard drive the main six components that help make up the inside are the head actuator , read/write actuator arm , read/write head , spindle , and platter DVD
Short for either Digital Versatile Disc or Digital Video Disc , DVD or DVD-ROM is a disc drive that allows for large amounts of data on one disc the size of a standard Compact Disc. DVD drives were first sold in 1997 and today are widely used for storing and viewing movies and other data. To play a DVD on a computer a user must have a DVD drive as well as a DVD player, which is a software program designed to play and control a DVD disc. The movie Twister became the first featured film put on DVD on March 25, 1996 .
Compact Disc
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Abbreviated as CD , a compact disc is a flat round storage medium that is read by a laser in a CD ROM drive that was first created by A Philips on August 17, 1982 . The standard CD is capable of holding 72 minutes of music or 650 MB of data. 80 minute CDs are also commonly used to store data and are capable of containing 700 MB data.
When referring to a round CD, DVD, or Blu ray it is known as a disc and not a disk.
Installing Different Storage Devices
Before installing storage devices, it is always a good idea to plan the positions of the devices in the device bays. Be sure not to mount the CD / DVD drive directly next to the hard disk drive, since the CD / DVD drive creates a magnetic field that can be strong enough to erase data on the hard drive. Also, be sure to locate and identify all cables and headers, and note the relative positions of each cable that will connect each device to the power supply, motherboard. It is always a good idea to mark the connectors with a felt tipped pen, or to draw a diagram, showing how the connections will be made.
Installing an IDE or SATA Hard Disk
Connecting Power Cables
There are three main types of power cables / connectors for storage devices...
• The berg connector is the smallest connector coming from the power supply (if one exists at all newer PCs that do not have a floppy disk may not include a berg connector at all).
• The molex connectors supply power to older (IDE style) hard disk / CD / DVD devices. PCs using IDE technology can normally accommodate 2 or 4 storage devices, and therefore, power supplies will usually include 2 or 4 molex connectors.
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• The SATA connectors supply power to newer (SATA style) hard disk / CD / DVD devices. PCs using SATA technology can normally accommodate 4 SATA storage devices, and therefore, power supplies will usually include 4 SATA connectors. (Older power supplies without SATA connectors can use an IDE SATA adapter).
Connecting Data Cables
There are two main types of data cables / connectors for storage devices ...
• Flat ribbon cables are used to connect the floppy disk drive to the motherboard, as well as older (IDE style) hard disk / CD / DVD devices. • The cable for the floppy disk drive will have a "twist" in one end. This end must be connected to the floppy disk drive. • The hard disk drive and CD ROM are often connected with a single, long cable that has a dual connector. The cable generally runs from the motherboard to the hard disk drive, and then to the CD ROM. The "master / slave" jumper on the devices should be set accordingly. • Ribbon cables usually have one red edge that should be lined up with "pins 1/2" on the device and motherboard headers. In general, pins 1/2 are the pin closest to the power connector on a hard disk drive and CD ROM, and are the pins farthest from the power connector on a floppy disk drive. (However, this is a general rule of thu mb, and is not always true ... check the specific device to see the exact markings for pins 1/2). • The connectors on ribbon cables often have one hole that is "filled" in, which will line up with one missing pin on the device or motherboard headers, as show n in the figure on the right. This is designed to help install the cable correctly. However, if the connector is not correctly aligned, pins on the header can be bent, and the device or motherboard
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permanently damaged.
• The SATA data connectors are used to connect newer (SATA style) hard disk / CD / DVD devices to the motherboard. PCs using SATA technology can normally accommodate 4 SATA storage devices, and therefore, motherboards will usually include 4 SATA headers. (Unlike the IDE ribbon cables, each SATA cable is used to connect a
single SATA device).
Mounting Devices
• In a tower case, the storage devices are usually screwed into metal rails in the device bay. When the screws are removed, the device slides out like the drawer in a cabinet, as shown on the right. Hard drives and some types of floppy disk drives will slide backward into the interior of the case,
whereas most CD ROMs are removed through the front of the case.
• Desktop cases are designed to save space, and so the storage devices are often more tightly packed and difficult to remove than in tower cases.
As with tower cases, many desktop cases have device bays with metal rails that the storage devices can slide in and out of. In addition, some devices are secured by a 4 sided "cage", and must be carefully lifted out as shown on the right.
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UNIT 4
Introduction to Electronics
Electronic Theory
Electronics is all about controlling the physical world. Physical objects have properties such as temperature, force, motion, sound/radio/light waves associated with them Electronic devices convert the physical world to electronic signals where some process is applied to these electronic signals and then they are converted back to the physical world where we can see the outcome of the process.
Take an example such as a television, the physical world radio signal on the input is converted to anelectronic signal, this is processed by the electronic circuit and converted to light which we see and sound we can hear.
What is electronics?
To put the tiny electrons to work is Electronics. The word ‘electronics’ is derived from electron mechanics. Electronics is the science and technology of the motion of electrons (or other such charges) in gas, vacuum, or in any semiconductor. It deals principally with the communication of information and/or data handling. Compared to the more established branches of engineering—civil, mechanical and electrical, the electronics is a newcomer—hardly 100 years old. Until around 1960, it was considered an integral
87 | P a g e part of electrical engineering. But due to the tremendous advancement over the last few decades, electronics has now gained its rightful place. The advancement has been so fast that many sub branches of electronics—such as Computer Science Engineering, Communication Engineering, Control and Instrumentation Engineering, Information Technology— are now full fledged courses in many universities. Everyone is familiar with electronic devices, be it the television, the computer, or then cellular phone. However, to most people, what goes on inside, is a mystery. An Electronics Engineer knows and understands the functioning of these devices. He acquires the capability to further improvise these devices as per the needs of the user. Electronics Engineering
History of electronics
Electronics took birth in 1897 when J.A. Fleming developed a vacuum diode. Useful electronics came in 1906 when vacuum triode was invented by Lee De Forest. This device could amplify electrical signals. Later, around 1925, tetrode and pentode tubes were developed. These tubes dominated the field of electronics till the end of World War II. The Transistor Era The era of semiconductor electronics began with the invention of the junction transistor in 1948. Bardeen, Brattain and Shockley were awarded the Nobel Prize in Physics in 1956 for this invention. This was the first Nobel award given for an engineering device in nearly 50 years. Soon, the transistors were replacing the bulky vacuum tubes in different electronic circuits. The tubes had major limitations : power was consumed even when they were not in use and filaments burnt out, requiring frequent tube replacements. By now, vacuum tubes have become history. Earlier, the transistors were made from germanium as it was easier to purify a sample of germanium. In 1954, silicon transistors were developed. These afforded operations upto 200 °C, whereas germanium device could work well only upto about 75 °C. Today, almost all semiconductor devices are fabricated using silicon. Invention of the Integrated Circuits (IC) In 1958, Kilby conceived the concept of building an entire electronic circuit on a single semiconductor chip. All active and passive components and their interconnections could be integrated on a single chip, during the manufacturing process. This drastically reduced the size and weight, as well as the cost per active component. The term ‘microelectronics’ refers to the design and fabrication of these high componentdensity ICs. The following approximate dates give some indication of the increasing component count per chip of area 3 × 5 mm2 and thickness 0.3 mm (about three times the thickness of human hair) :
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1951 — Discrete transistors
1960 — Small Scale Integration (SSI), fewer than 100 components
1966 — Medium Scale Integration (MSI), 100 to 1000 components
1969 — Large Scale Integration (LSI), 1000 to 10000 components
1975 — Very Large Scale Integration (VLSI), more than 10000 components
The Field-Effect Transistor (FET)
In 1951, Shockley proposed the junction field effect transistor (JFET), using the effect of applied electric field on the conductivity of a semiconductor. A reliable JFET was produced in 1958. The techniques to make reliable JFETs led to an even more important device called metaloxide semiconductor field effect transistor (MOSFET). Subsequent improvements in processing and device design, and the growth of the computer industry have made MOS devices the most widely used transistors. Introduction to Electronics 3 Digital Integrated Circuits The growth of computer industry spurred new IC development. In turn, the new IC concepts resulted in new computer architecture. Speed, power consumption, and component density are important considerations in digital ICs. Transistor transistor logic (TTL), emitter coupled logic (ECL) and integrated injection logic (I2L) technologies were developed. The use of MOSFETs is very attractive because very high component densities are obtainable. Originally, reliable fabrication employed PMOS devices, in which operation depended on hole flow. Improved fabrication methods led to the use of N channel MOS (NMOS).These gave higher speed performance. Later, the complementary metal oxide semiconductor (CMOS) technology employing both PMOS and NMOS in a circuit, was used. MOSFETs find major applications in semiconductor memories. Earlier in 1970s, bipolar junction transistors (BJTs) were used in making random access memories (RAMs), which were capable of both storing and retrieving data (i.e., writing and reading). These could store about 100 bits of information. Using MOS technology, 16000 bit RAMs were made available in 1973, 64000 bit RAMs in 1978, and 288000 bit in 1982. By now, you have more than a billion bit chips available. Read only memories (ROMs), used for look up tables in computers (e.g., to obtain the value of sin x), were first introduced in 1967. Subsequent developments led to programmable ROMs (PROMs) and erasable PROMs (EPROMs) in which data stored could be removed (erased) and new data stored. The first microprocessor (mP) was developed by M.E. Hoft at Intel in 1969. It led to the “computer on a chip”. Another important development arising from MOS technology is the charge coupled device (CCD). Recently, CCDs have found applications in camera manufacturing, image processing and communication. Analog Integrated Circuits The first operational amplifier (OP AMP) was developed in 1964. Since then the OP AMP has become the “workhorse” in analog
89 | P a g e signal processing. Other circuits and systems developed subsequently are analog multipliers, digital to analog (D/A) and analog to digital (A/D) converters, and active filters.Technological developments are taking place today at an awesome pace. To digest, to appreciate and to meet the challenges of these dynamic fields, it has become essential to equip oneself with the fundamental understanding of the subject.
Applications of electronics
Electronics is a big bag of tricks. It finds applications almost everywhere:
Communications and Entertainment
An audio amplifier is the heart of a tape recorder, a public address (PA) system, radio and television receiver. The video section of a TV reproduces the picture signal received. Many interesting toys use ICs. The telephone systems now employ digital ICs for switching and memory. Communication satellites became feasible because of microelectronics.
Electronics Engineering
A new era of electronics, called digital signal processing (DSP), has evolved because ICs have made the merging of communications and computation possible.
Controls and Instrumentation
Silicon controlled rectifiers (SCRs) are used in the speed control of motors, power rectifiers and inverters. Automation of industrial processes has been made possible by electronic circuits. With microelectronics, computers have become integral components of control systems. Very accurate and user friendly instruments like digital voltmeter (DVM), cathode ray oscilloscope (CRO), frequency counter, signal generator, strain gauge, pH meter, spectrum analysers, etc.,are now available.
Defense Applications
Defense services are using electronic equipments. Radar, sonar and infrared systems are used to detect the location of enemy jet fighters, war ships and submarines, and then to control the aiming and firing of guns. Guided missiles are completely controlled by electronic means. Electronic circuits providea means of secret communication between the head quarter and different units. Such acommunication has become absolutely essential to win a war.
Industrial Applications
Use of automatic control systems in different industries is increasing day by day. Control of thickness, quality, weight and moisture content of a material can be easily done by
90 | P a g e such systems. Use of computers has made the reservations in railways and airways simple and convenient. Even the power stations, which generate thousands of megawatts of electricity, are controlled by tiny electronic devices and circuits.
Medical Sciences
Doctors and scientists are finding new uses of electronic systems in the diagnosis and treatment of different ailments. Electrocardiographs (ECG), X rays, short wave diathermy units, ultrasound scanning machines, endoscopy, etc. are in common use. Even the thermometers, blood pressure measuring instruments, blood sugar measuring instruments, etc. are so userfriendly because of electronic circuits, that the patient can himself handle them. Different Types Electronic Components
Soldering electronic components
What is solder?
Solder is an alloy (mixture) of tin and lead, typically 60% tin and 40% lead. It melts at a temperature of about 200°C. Coating a surface with solder is called 'tinning' because of the tin content of solder. Lead is poisonous and you should always wash your hands after using solder.
Solder for electronics use contains tiny cores of flux, like the wires inside a mains flex. The flux is corrosive, like an acid, and
it cleans the metal surfaces as the solder melts. This is why you must melt the solder actually on the joint, not on the iron tip. Reels of solder Without flux most joints would fail because metals quickly oxidise and the solder itself will not flow properly onto a dirty, oxidised, metal surface.
The best size of solder for electronics is 22swg (swg = standard wire gauge).
Electronic Components
These pages are intended to help you to identify components, find out their values and learn about their function in circuits.
• Capacitors • Connectors and Cables • Diodes including zener diodes • Integrated Circuits (Chips)
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o 4000 series logic ICs (pin connections etc) o 74 series logic ICs (pin connections etc) • Lamps • LEDs (Light Emitting Diodes) • Relays • Resistors o Resistor Color Code Calculator • Switches • Transistors o Heat sinks for transistors • Variable Resistors • Other components including LDRs and thermistors How to Solder
First a few safety precautions:
• Never touch the element or tip of the soldering iron. They are very hot (about 400°C) and will give you a nasty burn.
• Take great care to avoid touching the mains flex with the tip of the iron. The iron should have a heatproof flex for extra protection. An ordinary plastic flex will melt immediately if touched by a hot iron and there is a serious risk of burns and electric shock.
• Always return the soldering iron to its stand when not in use. Never put it down on your workbench, even for a moment!
• Work in a well-ventilated area. The smoke formed as you melt solder is mostly from the flux and quite irritating. Avoid breathing it by keeping you head to the side of, not above, your work.
• Wash your hands after using solder. Solder contains lead which is a poisonous metal.
Preparing the soldering iron:
• Place the soldering iron in its stand and plug in. The iron will take a few minutes to reach its operating temperature of about 400°C.
• Dampen the sponge in the stand. The best way to do this is to lift it out the stand and hold it under a cold tap for a
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moment, then squeeze to remove excess water. It should be damp, not dripping wet.
• Wait a few minutes for the soldering iron to warm up. You can check if it is ready by trying to melt a little solder on the tip.
• Wipe the tip of the iron on the damp sponge. This will clean the tip.
• Melt a little solder on the tip of the iron. This is called 'tinning' and it will help the heat to flow from the iron's tip to the joint. It only needs to be done when you plug in the iron, and occasionally while soldering if you need to wipe the tip clean on the sponge.
You are now ready to start soldering:
Hold the soldering iron like a pen, near the base of the handle. Imagine you are going to write your name! Remember to never touch the hot element or tip.
• Touch the soldering iron onto the joint to be made. Make sure it touches both the component lead and the track. Hold the tip there for a few seconds and...
• Feed a little solder onto the joint. It should flow smoothly onto the lead and track to form a volcano shape as shown in the diagram. Apply the solder to the joint, not the iron.
• Remove the solder, then the iron, while keeping the joint still. Allow the joint a few seconds to cool before you move the circuit board.
• Inspect the joint closely. It should look shiny and have a 'volcano' shape. If not, you will need to reheat it and feed in a little more solder. This time ensure that both the lead and track are heated fully before applying solder.
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Using a heat sink
Some components, such as transistors, can be damaged by heat when soldering so if you are not an expert it is wise to use a heat sink clipped to the lead between the joint and the component body. Crocodile clip You can buy a special tool, but a standard crocodile clip works just as well and is cheaper Switching circuits
Circuit switching is a methodology of implementing a telecommunications network in which two network nodes establish a dedicated communications channel (circuit) through the network before the nodes may communicate. The circuit guarantees the full bandwidth of the channel and remains connected for the duration of the communication session. The circuit functions as if the nodes were physically connected as with an electrical circuit.
The defining example of a circuit switched network is the early analog telephone network. When a call is made from one telephone to another, switches within the telephone exchanges create a continuous wire circuit between the two telephones, for as long as the call lasts.
Circuit switching contrasts with packet switching which divides the data to be transmitted into packets transmitted through the network independently. Packet switching shares available network bandwidth between multiple communication sessions.
In circuit switching, the bit delay is constant during a connection, as opposed to packet switching, where packet queues may cause varying packet transfer delay. Each circuit cannot be used by other callers until the circuit is released and a new connection is set up. Even if no actual communication is taking place, the channel remains unavailable to other users. Channels that are available for new calls are said to be idle.
Virtual circuit switching is a packet switching technology that emulates circuit switching, in the sense that the connection is established before any packets are transferred, and packets are delivered in order.
While circuit switching is commonly used for connecting voice circuits, the concept of a dedicated path persisting between two communicating parties or nodes can be extended to signal content other than voice. Its advantage is that it provides for continuous transfer without the overhead associated with packets making maximal use of available bandwidth for that communication. The disadvantage is inflexibility; the
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Power electronics and Digital electronics
Power electronics is the application of solid state electronics for the control and conversion of electric power.
Power electronic converters can be found wherever there is a need to modify a form of electrical energy (i.e. change its voltage, current or frequency). The power range of these converters is from some milliwatts (as in a mobile phone) to hundreds of megawatts (e.g. in a HVDC transmission system). With "classical" electronics, electrical currents and voltage are used to carry information, whereas with power electronics, they carry power. Thus, the main metric of power electronics becomes the efficiency.
The first very high power electronic devices were mercury arc valves. In modern systems the conversion is performed with semiconductor switching devices such as diodes, thyristors and transistors. In contrast to electronic systems concerned with transmission and processing of signals and data, in power electronics substantial amounts of electrical energy are processed. An AC/DC converter (rectifier) is the most typical power electronics device found in many consumer electronic devices, e.g. television sets, personal computers, battery chargers, etc. The power range is typically from tens of watts to several hundred watts. In industry the most common application is the variable speed drive (VSD) that is used to control an induction motor. The power range of VSDs start from a few hundred watts and end at tens of megawatts.
The power conversion systems can be classified according to the type of the input and output power
• AC to DC (rectifier)
• DC to AC (inverter)
• DC to DC (DC to DC converter)
• AC to AC (AC to AC converter)
Digital electronics
Digital electronics represent signals by discrete bands of analog levels , rather than by a continuous range. All levels within a band represent the same signal state. Relatively small changes to the analog signal levels due to manufacturing tolerance , signal attenuation or parasitic noise do not leave the discrete envelope, and as a result are ignored by signal state sensing circuitry.
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In most cases the number of these states is two, and they are represented by two voltage bands: one near a reference value (typically termed as "ground" or zero volts) and a value near the supply voltage, corresponding to the "false" ("0") and "true" ("1") values of the Boolean domain respectively.
Digital techniques are useful because it is easier to get an electronic device to switch into one of a number of known states than to accurately reproduce a continuous range of values.
Digital electronic circuits are usually made from large assemblies of logic gates , simple electronic representations of Boolean logic functions .
Three digital circuits, showing progressing miniaturization
• A binary clock , hand wired on breadboards
• An industrial digital controller
• Intel 80486DX2 microprocessor
Electrical and Electronics engineering are two popular engineering streams in India. Electrical is one of the oldest branch along with mechanical and civil. Electronics is one of the modern streams, which has become popular during the last two decades.
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Difference between electrical and electronics
Electrical Engineering
This is one of the oldest branches of Engineering. It deals with the study of the application of principles of electricity and electromagnetism. There are so many branches that come as a part of electrical engineering. Electronics, telecommunication, instrumentation, etc are some of them. The course offered at most colleges briefly touches all these areas. The first year of the engineering course has mostly common subjects for all branches. It deals with subjects like math, physics, chemistry, drawing, basics on electrical, electronic and mechanical engineering and a paper on computer programming. Math is one of the subjects that an electrical engineering student will learn throughout the course. There will be papers on mechanical engineering during the next three to four semesters. During the second semester, there will be papers on network systems, material science, electrical circuit theory and electronic devices and circuits. Electrical machines papers start from the fourth semester onwards and continue till the end. Electromagnetic theory, digital systems, etc are also papers of the fourth semester. The course proceeds to control systems, power systems and communication systems in the fifth semester. There are more papers on drawing like machine drawing in the sixth semester. It will also have papers on power electronics, microprocessor, VLSI technology in the sixth semester. There are also a few industrial management and engineering economics papers during the final year. Other papers that would be dealt with throughout the second half of the course are control systems, power systems, etc. Each university/college has a set of electives to choose from during the last year. There are also practical papers for all semesters. The final project is also a very important part of the curriculum.
Electronics Engineering
Electronics engineering is that branch of Electrical engineering that deals with the study of electronic components, devices like diodes, transistors, etc. The course structure during the first three semesters is pretty much the same as that of electrical engineering. During the fourth semester, the course deals with data structures, signals and systems, digital electronics and instrumentation. The fifth semester has papers on industrial electronics, electronic circuit design, communication systems and automatic control systems. Digital signal processing, microprocessor, VLSI technology are papers dealt with during the sixth semester. The rest of course structure is the same as that of electrical engineering course. There are electives to be chosen from during the final year. Again, the final project is important
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Concepts current- résistance - voltage
Electrostatics is the study of the effects when the electrical charges are at rest. The term electric current is used to describe the flow of charge through some region in space. It is defined as the rate at which electric charge flows through a point. If ∆ Q is the amount of charge that passes through an area in time interval ∆ t, then the current over that time interval is the ratio of the charge to the time interval. Its S.I. unit is ampere.
I = ∆ Q / ∆ t.
Conventionally, we define the direction of the current as the direction of flow of positive charge. regardless of the sign of the actual charged particles in motion. the direction of current is opposite to the direction of flow of electrons.
When a potential difference is applied across the conductor, an electric field is established in the conductor. The electric field exerts an electric force on the electrons. This force accelerates the electrons and hence produces a current.
Resistance R:
The battery is the energy source or the external agent. Its energy get transformed as the kinetic energy of the electrons. When the electrons strike the metal atoms, some of the kinetic energy is transferred to the atoms, which heats the wire. This opposition experienced by the electrons in their motion is known as resistance R. Its S.I. unit is Ohms.
Resistor:
The circuit element which controls the flow of electrons in the wire by opposing their motion is called the resistor. If resistance for a given voltage increases, then the current decreases.
R = ∆ V / I, where ∆ V = Applied potential difference and I = current.
Resistance of a wire is found to be proportional to the length and inversely proportional to its cross sectional area.
R = ρ (l/A), where the constant of proportionality ρ is called as resistivity. Its S.I. unit is ohm. meter. Inverse of resistivity is called conductivity.
Resistors in Series:
when resistors are joined in series, the total resistance R of the combination is equal to the sum of the individual resistances, i,e,
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R = R 1 + R 2 + R 3 + —————— + R n.
The current is the same in all resistors. The total potential difference across the combination is equal to the sum of the potential differences across the individual resistors.
Resistors in Parallel:
When resistors are connected in parallel, the effective resistance of the combination is given by
1 / R = 1 / R 1 + 1 / R 2 + 1 / R 3 + ———————— + 1 / R n.
The potential difference is the same across each resistor. the total current is equal to the sum of the currents in the individual resistances.
Voltage Concepts
In electrical fields, we will want to think in terms of the potential energy per unit of charge. Near the earth's surface the potential energy of a mass, m, h meters above the surface is mgh. The potential energy per unit mass is just gh. Voltage is the potential energy per unit charge for a charge in an electrical force field.
There are consequences of the inverse square law for electrical forces. Generally, those consequences are similar to what happens in gravitational systems.
• In an electrical field, or in any conservative field like a gravitational field, we will have to do the same amount of work to move the charge between any two points A and B, no matter what path we take in moving the charge. Work done in a conservative field is said to be "path independent".
• The potential energy in a gravitational field and the voltage in an electrical field (potential energy per unit of charge) are functions of position only.
One important consequence is a relationship between energy put into a charge as it moves.
• If we move a charge from point A to point B, and put a given number of joules of work into the charge, we will recover exactly the same number of joules from the charge if it moves back from point B to point A. If we move the charge through any closed path or circuit, there will be no net energy input to the system and no net energy recovered from the charge.
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• If we move a charge from point A to point B, the number of joules of work we put into the charge can be calculated by multiplying the charge, Q, by the voltage
difference between points A and B, V ab . Types current and their conversion
There are two types of electric current: direct current (DC) and alternating current (AC). The electrons in direct current flow in one direction. The current produced by a battery is direct current. The electrons in alternating current flow in one direction, then in the opposite direction—over and over again. In the United States, the current flow alternates 120 times per second. (In Europe it alternates 100 times per second.) The current supplied to your home by the local utility is alternating current.
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UNIT 5
MICROPROCESSOR
The microprocessor is the combination of solid – state technology development and the advancing computer technologies which came together in the early 1970s. With the low cost of a device and the flexibility of a computer, microprocessor is a product which performs both control and processing functions. A brief history
The microprocessor of two major technologies; digital computer and solid – state circuits. These two technologies came together in the early 1970s, allowing engineers to produce the microprocessor.
The digital computer is a set of digital circuit controlled by a program that makes it do the job you want done. The program tells the digital how to move process data. It does this by using the digital computer’s calculating logic, memory circuits, and I/O devices. The way the digital computer’s logic circuits are put together to build the calculating logic, memory circuits, and I/O devices is called its architecture. The microprocessor is like the digital computer because both do computations under programming control.
Figure 1 1 shows the major events in the two technologies as they developed over the last five decades from the days of World War II.
During World War II, scientists developed computers for military use. The latter half of the 1994s, digital computer was developed to do scientific and business work, Electronic circuit technology also advanced during World War II. Radar work increased the understanding of fast digital circuits called pulse circuits. After the war, scientists made great progress in solid state physics. Scientists at Bell Laboratories invented the transistor, a solid state device, in 1948.
In the early 1950s, the first general purpose digital computer appeared. Vacuum tubes were used for active electronic components. They were used to build basic logic circuits such as gates and flip flops. Vacuum tubes also formed part of the machines built to communicate with the computer – the I/O (input/output) devices. The first digital computers were huge, because the vacuum tubes were hot and required air conditioning. Vacuum tubes made the early computer expensive to run and maintain.
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Solid state circuit technology also made great strides during the 1950s. The knowledge of semiconductors increased. The use of silicon lowered costs, because silicon is much more plentiful than germanium, which had been the chief material for making the early semiconductors. Mass production methods made transistors common and inexpensive.
In the late 1950s, the designers of digital computers jumped at the chance to replace vacuum tubes with transistors.
In the early 1960s, the art of building solid state computers was divided in two directions. The first direction was building huge solid state computer by IBM. IT still required large, air conditioned rooms and very complicated. IT could process large amounts of data. These large data processing systems were used for commercial and scientific application.
The big computer was still very expensive. In order to pay for it had to be run 24 hours a day, 7 days a week. Another direction of development is began building small computers. These minicomputers were not as powerful as their larger relatives, but they were not as expensive either. And they still performed many useful functions. By the early 1960s, the semiconductor industry found a way to put a number of transistors on one silicon wafer. The transistors are connected together with small metal traces. When the transistors are connected together, they become a circuit which performs a function, such as a gate, flip flop, register, or adder. This new technology created basic semiconductor building blocks. The building blocks or circuit modules made this way are called an integrated circuit (IC).
By the mid 1960s, the technology of ICs pushed to develop low cost manufacturing techniques. The use of ICs let minicomputers become more and more powerful for their size. The desk sized minicomputers of the 1960s became as powerful as a room sized computer of the late 1950s. Now $10,000, drawer sized minicomputers were as powerful as the older $100,000.
The late 1960s and early 1970, large scale integration (LSI) become common. Large scale integration was making it possible to produce more and more digital circuits in a single IC.
By the 1980s, very large scale integration (VLSI) gave us ICs with over 100,000 transistors. By the mid 1970s, LSI had reduced the calculator to a single circuit. After the calculator was reducing, the next natural step was to reduce the architecture of the
102 | P a g e computer to a single IC. The microprocessor was the resulting circuit of achievement. The microprocessor made possible the manufacture of powerful calculators and many other products. Microprocessor could be programmed to carry out a single task> Products like microwave ovens, telephone dialers and automatic temperature control systems become commonplace.
The early microprocessor processed digital data 4 bits (4 binary digits) at a time. These microprocessors were slow and did not compare to minicomputers. But new generations of microprocessors came fast. The 4 bit microprocessors grew into 8 bit microprocessors, then into 16 bit microprocessors, and then into 32 bit microprocessors. During the early 1980s, complete 8 bit microprocessor systems (microprocessors with memory and communications ability) were developed. These microcontrollers, or single chip microprocessors, have become popular as the basis of controllers for keyboards, VCRs, TVs, microwave ovens, smart telephones, and a host of other industrial and consumer electronic devices
Three major differences between microprocessors. The length of the microprocessor’s data word. The size of the memory which the microprocessor can directly address. The speed which the microprocessor can execute instructions.
Some of additional architectural differences are: The number of register available to the programmer. The different types of register available to the programmer. The different types of instructions available to the programmer. The different types of memory addressing modes available to the programmer. The different types of support circuits available to the system designer. Compatibility with readily available development, system and applications software. Compatibility with hardware development systems.
These differences make some microprocessors better for some applications and some other microprocessors better for other applications. Some microprocessors are better because they appeal to the user more than another which might work equally well in the same situation.
Bus
To transfer information internally, computers use buses. Buses are groups of conductors that connect the functional areas to one another. This is how the
103 | P a g e functional areas communicate with each other. A bus is a parallel data communication path over which information is transferred a byte or word at a time. The buses contain logic that the CPU controls. The items controlled are the transfer of data, instructions, and commands between the functional areas of the computer: CPU, memory, and I/O The type of information is generally similar on all computers; only the names or terminology of the bus types differs. The name of the bus or its operation usually implies the type of signal it carries or method of operation. The direction of signal flow for the different buses is indicated on figures in the computer’s technical manuals. The direction may be unidirectional or bidirectional depending on the type of bus and type of computer. Consult the computer’s technical manual for details. After becoming familiar with the basic functions and operations of buses, you’ll see that regardless of the names, their basic concepts are consistent throughout the computer. They provide avenues for information to be exchanged inside the computer.
BUS TYPES
The preferred method for data/information transfer between system components is by a common data bus. Where point to point data transfer is required, the digital format is the preferred method. General Requirements for Electronic Equipment Specifications, MIL STD 2036 series, provides a list of the industry accepted standard internal data buses. They include the standard and the interface as follows:
IEEE 696—IEEE Standard 696 Interface Devices, S 100 IEEE 896. l—IEEE Standard Backplane Bus Specification for Multiprocessor Architecture, Future Bus
I E E E 9 6 1 — S t a n d a r d f o r a n 8 b i t Microcomputer Bus System, STD Bus
IEEE 1014—Standard for a Versatile Backplane Bus, VMEbus
IEEE 1196—Standard for a Simple 32 Bit Backplane Bus, NuBus
IEEE 1296—Standard for a High Performance Synchronous 32 Bit Bus, Multibus II
All computers use three types of basic buses. The name of the bus is generally determined by the type of signal it is carrying or the method of operation. We group the buses into three areas as you see them in their most common uses. They are as follows: Control (also called timing and control bus), address, and data (also called a memory bus) buses Instruction (I), Operand (O), Input/Output Memory (I/O MEM) or
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Input/Output Controller (IOC), and Computer Interconnection System (CIS) Time multiplexed bus
Control Bus
The control bus is used by the CPU to direct and monitor the actions of the other functional areas of the computer. It is used to transmit a variety of individual signals (read, write, interrupt, acknowledge, and so forth) necessary to control and coordinate the operations of the computer. The individual signals transmitted over the control bus and their functions are covered in the appropriate functional area description. Address Bus
The address bus consists of all the signals necessary to define any of the possible memory address locations within the computer, or for modular memories any of the possible memory address locations within a module. An address is defined as a label, symbol, or other set of characters used to designate a location or register where information is stored. Before data or instructions can be written into or read from memory by the CPU or I/O sections, an address must be transmitted to memory over the address bus.
Data Bus
The bidirectional data bus, sometimes called the memory bus, handles the transfer of all data and instructions between functional areas of the computer. The bidirectional data bus can only transmit in one direction at a time. The data bus is used to transfer instructions from memory to the CPU for execution. It carries data (operands) to and from the CPU and memory as required by instruction translation. The data bus is also used to transfer data between memory and the I/O section during input/output operations. The information on the data bus is either written into memory at the address defined by the address bus or consists of data read from the memory address specified by the address bus. Figure 5 17 is an example of a computer’s bus system; control, address, and data buses.
Instruction (I) Bus
The instruction (I) bus allows communication between the CPU and memory. It carries to the CPU the program instruction words to be operated on by the CPU from memory or returns instructions to memory. The I bus is controlled by the CPU. It is capable of sending or receiving data while the operand(O) bus is receiving or sending data at the same time, but only in one direction at a time.
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Operand (O) Bus
The operand (O) bus allows communication between the CPU and memory or the CPU and an I/O Controller (IOC). The CPU controls the operation in both cases. The O bus is capable of sending or receiving data, while the I bus is receiving or sending data at the same time, but only in one direction at a time. The direction of the data depends on whether the CPU is reading data from memory or data is being written back into memory.
I/O MEM Bus or Input/Output Controller (IOC) BUS
The I/O memory bus allows communication between an I/O controller (IOC) and memory. It Is controlled by the IOC. To respond to the CPU, the I/O MEM bus must use the O bus. Figure 5 18 is an illustration of communications between a CPU, memory, and an IOC without a computer interconnection system. Pay close attention to the direction of signal flow and which buses allow communication between functional areas.
Computer Interconnection System
The Computer Interconnection System (CIS) provides the complete functional replication of the computer intraconnection among CPUs, IOCs, and memories in separate computers. This allows the internal buses to be extended beyond their own enclosure. The CIS consists of two independent halves: the requestor
106 | P a g e extension interface (REI) and the direct memory interface (DMI). REQUESTOR EXTENSION INTERFACE (REI).— The requestor extension interface (REI) is a bus extender. It extends the bus up to 15 other computer cabinets providing an interconnected system of memory modules, CPUs, and IOCs. The REI takes the requests from the requestor ports and goes through a priority network to determine the order in which it is to respond to the requestors. Once the REI has responded to a request, it puts the address onto the output bus, parity, and examines a code to determine the correct sequence. After the sequence is established, the REI broadcasts the requests and the address to all DMIs connected to it. The signals on the REI external interface are expanded to guarantee capture at the DMI operating synchronously to the REI, which can be located up to 500 cable feet away. Once the REI makes a request, it can send write data if it is performing a write operation or wait for a response and pass it to the requestor. The REI responds to the requestor just as memory does, including faults and aborts (terminates a process before it is completed).
DIRECT MEMORY INTERFACE (DMI) BUS.
The Direct memory interface is a responder or slave on the REI bus. The DMI bus is used in some computers that use an I, O, and IOC bus. The DMI bus is used to send requests from other enclosures (computers) to the module (CPU or IOC) requested. It acts as the requestor and makes requests to the CPU. When it requests an IOC, it uses IOC read and write requests. When it requests memory, it uses operand read or write, instruction read, or replace.
Time Multiplexed Bus
Another variation of the address and data bus is the time multiplexed bus. This single bus transmits both addresses and data using a four cycle clock (t1, t2, t3, and t4). The address is transmitted during the t1 clock cycle, the direction of data movement is selected during t2, and the data is transmitted during t3 and t4.
CPU Generation
AMD
Processor Year Bus widthDescription
29000 1988 32 32 bit embedded RISC microprocessor
29030 199? 32 32 bit embedded RISC microprocessor
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32 bit high performance embedded RISC 29040 199? 32 microprocessor
32 bit embedded RISC microprocessor with 29050 1990 32 integrated FPU
K5 1996 32 Pentium class processor
K6 1997 32 Pentium/Pentium II class processor
K6 2 1998 32 Pentium II class processor, enhanced version of K6
Pentium II class processor, enhanced version of K6 K6 III 1999 32 2
K7 1999 32 Pentium III/IV class processor
K8 2003 64 Eighth generation of x86 processors
K10 2007 64 Ninth generation of x86 processors
Bobcat 2011 64 Family of low power x86 microprocessors
Bulldozer 2011 64 Family of high performance x86 microprocessors
ARM
Processor Year Bus widthDescription
SA 110 19?? 32 Low power embedded StrongARM microprocessor
Cyrix
Processor Year Bus widthDescription
5x86 199? 32 80486/Pentium class processor
6x86 199? 32 Pentium/Pentium II class processor
Highly integrated Pentium/Pentium II class GX1 199? 32 processor
Highly integrated Pentium/Pentium II class GXm 199? 32 processor
MII 199? 32 Pentium II class processor
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Enhanced version of MediaGX processor (never MXi 32 released)
Digital Equipment Corporation
Processor Year Bus widthDescription
21064 199? 64 21064 and 21064A RISC processors
Ferranti
Processor Year Bus widthDescription
F100 L 1976 16 Bipolar microprocessor for military applications
IDT
Processor Year Bus widthDescription
Winchip C6 199? 32 Pentium class processor
Winchip 2 199? 32 Pentium II class processor
Intel
Processor Year Bus widthDescription
4004 1971 4 First microprocessor.
4040 1972 4 Enhanced version of the Intel 4004 processor.
8008 1972 8 First 8 bit microprocessor.
8080 1974 8 Successor to Intel 8008 CPU.
8085 1976 8 Enhanced version of Intel 8080 CPU.
8086 1978 16 First generation of Intel 80x86 processors.
8088 1979 8/16 8 bit (external) version of Intel 8086 CPU.
Next generation of 80x86 processors. Used mostly 80186 1982 16 as embedded processor.
Next generation of 80x86 processors. Used mostly 80188 1982 8/16 as embedded processor.
80286 1982 16 Second generation of 80x86 processors:
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new instructions, protected mode, support for 16MB of memory.
Embedded 32 bit microprocessor based on Intel 80376 1989 32 80386.
Third generation of 80x86 processors: 32 bit 80386 1985 32 architecture, new processor modes.
Fourth generation of 80x86 processors: integrated 80486 1989 32 FPU, internal clock multiplier.
Overdrive/Upgrade processors for Intel 80486 80486 overdrive 19?? 32 family.
Fifth generation of x86 processors: superscalar Pentium 1993 32 architecture, MMX.
Pentium II 1997 32 Sixth generation of x86 processors.
Low cost version of Pentium II, Pentium III and Celeron 1998 32 Pentium 4 processors.
Low cost microprocessor with integrated peripherals Timna 32 (never released)
Pentium III 1999 32 Enhanced and faster version of Pentium II.
Pentium 4 2000 32, 64 New generation of Pentium processors.
Pentium microprocessor specifically designed for Pentium M 2003 32 mobile applications
Celeron D 2004 32, 64 Low cost version Pentium 4 desktop processors.
Low cost microprocessor specifically designed for Celeron M 2004 32 mobile applications
Pentium D 2005 64 Dual core CPUs based on Pentium 4 architecture.
Pentium 2005 64 Dual core CPUs based on Pentium 4 architecture. Extreme Edition
Xeon 200? 32, 64 High performance version of Pentium 4 CPU.
80860 1989 32 Embedded 32 bit microprocessor with integrated 3D
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graphics.
80960 1988? 32 Embedded 32 bit microprocessor.
Itanium 2001 64 High performance 64 bit microprocessor.
Itanium 2 2002 64 High performance 64 bit microprocessor.
Core Solo 2006 32 32 bit single core microprocessor.
Core Duo 2006 32 32 bit dual core microprocessor.
Core 2 2006 64 64 bit microprocessor.
Pentium Dual 2007 64 64 bit low cost microprocessor. Core
Celeron Dual 2008 64 64 bit low cost microprocessor. Core
Atom 2008 32, 64 Ultra low power microprocessor.
Core i7 2008 32, 64 64 bit microprocessor.
Core i5 2009 32, 64 64 bit microprocessor.
Core i3 2010 32, 64 64 bit microprocessor.
Intersil
Processor Year Bus widthDescription
6100 19?? 12 CMOS microprocessor
MIPS Technologies
Processor Year Bus widthDescription
R3000 1988 32 32 bit RISC microprocessor.
R4000 1991 64 RISC processor.
R4400 1993 64 Enhanced version of R4000 RISC processor.
R4600 199? 64 Enhanced version of R4400PC RISC processor.
R5000 1996 64 Super scalar 64 bit RISC microprocessor
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R10000 199? 64 Super scalar 64 bit RISC microprocessor
MOS Technology
Processor Year Bus widthDescription
650x 1975 8 Very popular version of 8 bit processor.
Motorola
Processor Year Bus widthDescription
6800 1974 8 6800 microprocessor.
6809 197? 8 Enhanced version of 6800 microprocessor.
MC14500B 197? 1 Industrial Control Unit
First generation of Motorola 680x0 series of 68000 1979 16/32 processors.
First generation of Motorola 680x0 series of 68008 19?? 8/32 processors.
Second generation of Motorola 680x0 series of 68010 1982 16/32 processors.
Second generation of Motorola 680x0 series of 68012 198? 16/32 processors.
Third generation of Motorola 680x0 series of 68020 1984 32 processors.
Fourth generation of Motorola 680x0 series of 68030 1987 32 processors.
Fifth generation of Motorola 680x0 series of 68040 1991 32 processors.
Sixth generation of Motorola 680x0 series of 68060 1994 32 processors.
PowerPC 603 199? 32 RISC microprocessor
National Semiconductor
Processor Year Bus widthDescription
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PACE 1974 16 16 bit PMOS microprocessor
SC/MP 1976 8 8 bit microprocessor
INS8900 197? 16 16 bit NMOS microprocessor
SC/MP II 19?? 8 8 bit microprocessor
NSC800 198? 8 Z80 compatible microprocessor
32016 19?? 16/32 32 bit microprocessor with 16 bit data bus
NEC
Processor Year Bus widthDescription
8088 compatible processor with 8080 emulation V20 1984 8/16 mode.
8086 compatible processor with 8080 emulation V30 1984 16 mode.
8088 compatible processor with integrated V40 198? 8/16 peripherals and 8080 emulation mode.
8086 compatible processor with integrated V50 198? 16 peripherals and 8080 emulation mode.
NexGen
Processor Year Bus widthDescription
Nx586 19?? 32 Pentium class processor.
RCA
Processor Year Bus widthDescription
8 bit microprocessor from RCA. Includes 1802, 1802 197? 8 1804 and 1806.
Rise Technology
Processor Year Bus widthDescription
MP6 19?? 32 Pentium class processor.
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Signetics
Processor Year Bus widthDescription
2650 197? 8 8 bit processor
8X300 197? 8 8 bit RISC like microprocessor
Sun Microsystems
Processor Year Bus widthDescription
UltraSparc II 1996? 64 Second generation of UltraSparc processors
UltraSparc IIi 199? 64 Second generation of UltraSparc processors
UltraSparc III 199? 64 Third generation of UltraSparc processors
Texas Instruments
Processor Year Bus widthDescription
TMS9900 1976? 16 16 bit microprocessor
TMS9980 197? 16 16 bit microprocessor with 8 bit data bus
Enhanced version of TMS9995 16 bit TMS99105 1981 16 microprocessor
Enhanced version of TMS9995 16 bit TMS99110 1981 16 microprocessor
Transmeta
Processor Year Bus widthDescription
TM5600 19?? 32 Low power microprocessor.
TM5800 2001 32 Low power microprocessor.
USSR
Processor Year Bus widthDescription
1801 198? 16 DEC (PDP 11) compatible microprocessor
VIA
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Processor Year Bus widthDescription
Cyrix III (C3) 2000 32 Pentium/Pentium II class processor
Embedded ultra low power x86 compatible Eden ESP 19?? 32 microprocessor
C7 M 2005 32 Low power mobile microprocessor
C7 D 2006 32 Low power desktop microprocessor
Western Design Center
Processor Year Bus widthDescription
65816 19?? 16 16 bit microprocessor with 6502 emulation mode
Western Electric
Processor Year Bus widthDescription
WE 32100 1985? 32 32 bit microprocessor
WE 32200 198? 32 32 bit microprocessor
Zilog
Processor Year Bus widthDescription
Improved version of Intel 8080 processor: new Z80 1976 8 instructions.
Z800x 1979? 16 16 bit microprocessor.
Z180 19?? 8 High integration version of Z80 processor.
The term "x86" can refer both to an instruction set architecture and to microprocessors which implement it.
The x86 instruction set architecture originated at Intel and has evolved over time by the addition of new instructions as well as the expansion to 64 bits. As of 2009, x86 primarily refers to IA 32 (Intel Architecture, 32 bit) and/or x86 64 , the extension to 64 bit computing.
Versions of the x86 instruction set architecture have been implemented by Intel, AMD and several other vendors with each vendor having its own family of x86 processors.
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8086/8087 (1978)
The 8086 was the original x86 microprocessor, with the 8087 as its floating point coprocessor. The 8086 was Intel's first 16 bit microprocessor. 8088 (1979)
After the development of the 8086, Intel also created the lower cost 8088. The 8088 was similar to the 8086, but with an 8 bit data bus instead of a 16 bit bus.
80186/80187 (1982)
The 186 was the second Intel chip in the family; the 80187 was its floating point coprocessor. Except for the addition of some new instructions, optimization of some old ones, and an increase in the clock speed, this processor was identical to the 8086.
80286/80287 (1982)
The 286 was the third model in the family; the 80287 was its floating point coprocessor. The 286 introduced the “Protected Mode” mode of operation, as opposed to the “Real Mode” that the earlier models used. All subsequent x86 chips can also be made to run in real mode or in protected mode.
80386 (1985)
The 386 was the fourth model in the family. It was the first Intel microprocessor with a 32 bit word. The 386DX model was the original 386 chip, and the 386SX model was an economy model that used the same instruction set, but which only had a 16 bit bus. The 386EX model is still used today in embedded systems.
80486 (1989)
The 486 was the fifth model in the family. It had an integrated floating point unit for the first time in x86 history. Early model 80486 DX chips were found to have defective FPUs. They were physically modified to disconnect the FPU portion of the chip and sold as the 486SX (486 SX15, 486 SX20, and 486 SX25). A 487 "math coprocessor" was available to 486SX users and was essentially a 486DX with a working FPU and an extra pin added. The arrival of the 486DX 50 processor saw the widespread introduction of fanless heat sinks being used to keep the processors from overheating.
Pentium (1993)
Intel called it the “Pentium” because they couldn't trademark the code number “80586”. The original Pentium was a faster chip than the 486 with a few other enhancements; later models also integrated the MMX instruction set.
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Pentium Pro (1995)
The Pentium Pro was the sixth generation architecture microprocessor, originally intended to replace the original Pentium in a full range of applications, but later reduced to a more narrow role as a server and high end desktop chip.
Pentium II (1997)
The Pentium II was based on a modified version of the P6 core first used for the Pentium Pro, but with improved 16 bit performance and the addition of the MMX SIMD instruction set, which had already been introduced on the Pentium MMX.
Pentium III (1999)
Initial versions of the Pentium III were very similar to the earlier Pentium II, the most notable difference being the addition of SSE instructions.
Pentium 4 (2000)
The Pentium 4 had a new 7th generation "NetBurst" architecture. It is currently the fastest x86 chip on the market with respect to clock speed, capable of up to 3.8 GHz. Pentium 4 chips also introduced the notions “Hyper Threading”, and “Multi Core” chips.
Core (2006)
The architecture of the Core processors was actually an even more advanced version of the 6th generation architecture dating back to the 1995 Pentium Pro. The limitations of the NetBurst architecture, especially in mobile applications, were too great to justify creation of more NetBurst processors. The Core processors were designed to operate more efficiently with a lower clock speed. All Core branded processors had two processing cores; the Core Solos had one core disabled, while the Core Duos used both processors.
Core 2 (2006)
An upgraded, 64 bit version of the Core architecture. All desktop versions are multi core.
i Series (2008)
The successor to Core 2 processors featuring Hyper Threading.
Celeron (first model 1998)
The Celeron chip is actually a large number of different chip designs, depending on price. Celeron chips are the economy line of chips, and are frequently cheaper than the
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Pentium chips—even if the Celeron model in question is based off a Pentium architecture.
Xeon (first model 1998)
The Xeon processors are modern Intel processors made for servers, which have a much larger cache (measured in megabytes in comparison to other chips' kilobyte sized cache) than the Pentium microprocessors.
AMD x86 Compatible Microprocessors
Athlon
Athlon is the brand name applied to a series of different x86 processors designed and manufactured by AMD. The original Athlon, or Athlon Classic, was the first seventh generation x86 processor and, in a first, retained the initial performance lead it had over Intel's competing processors for a significant period of time.
Turion
Turion 64 is the brand name AMD applies to its 64 bit low power (mobile) processors. Turion 64 processors (but not Turion 64 X2 processors) are compatible with AMD's Socket 754 and are equipped with 512 or 1024 KiB of L2 cache, a 64 bit single channel on die memory controller, and an 800 MHz HyperTransport bus.
Duron
The AMD Duron was an x86 compatible computer processor manufactured by AMD. It was released as a low cost alternative to AMD's own Athlon processor and the Pentium III and Celeron processor lines from rival Intel.
Sempron
Sempron is, as of 2006, AMD's entry level desktop CPU, replacing the Duron processor and competing against Intel's Celeron D processor.
Opteron
The AMD Opteron is the first eighth generation x86 processor (K8 core), and the first of AMD's AMD64 (x86 64) processors. It is intended to compete in the server market, particularly in the same segment as the Intel Xeon processor. Definition of: MHz
(Mega Hert Z) One million cycles per second. It is used to measure the transmission
118 | P a g e speed of electronic devices, including channels, buses and the computer's internal clock. A one megahertz clock (1 MHz) means some number of bits (16, 32, 64, etc.) are manipulated one million times per second. A one gigahertz clock (1 GHz) means one billion times.
MHz and GHz are used to measure the speed of the CPU. For example, a 1.6 GHz computer processes data internally (calculates, compares, etc.) twice as fast as an 800 MHz machine. However, the doubled clock speed of the CPU does not mean twice as much finished work gets done in the same time frame. Internal cache design, bus speed, disk speed, network speed and software design all contribute to the computer's overall processing speed and performance (overall throughput).
Users are often dismayed to find that they only obtain incremental improvements after purchasing a computer rated much faster than their old one. In addition, newer versions of software are often less efficient than previous ones. A faster computer is often required just to maintain the same performance level as the old software. See MIPS , Hertz and space/time .
MHz and GHz Are the Heartbeat When referencing CPU speed, the megahertz and gigahertz ratings are really the heartbeat of the computer, providing the raw, steady pulses that energize the circuits. If you know German, it is easy to remember. The word "Herz," pronounced "hayrtz," means heart. This was a coincidence, because in 1883, Heinrich Hertz identified electromagnetic waves.
Definition of: GHz
(Giga Hert Z) One billion cycles per second. High speed computers have internal clocks rated in GHz, and radio frequency applications transmit in this range. See MHz for an explanation of how GHz and MHz affect computer performance. See RF and space/time .
Motherboard is the most important component of a system. It is a Printed Circuit Board (PCB) where all the components of a system are connected. The Central Processing Unit (CPU), hard drives, memory and every other part of a system is connected to the motherboard by means of slots, connectors and sockets. The motherboard chipset is a series of chips that are a part of the motherboard. Types of Motherboards Motherboards and the capacity and efficiency of motherboards differ according to the type of system you use.
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Motherboards are classified as integrated and Non integrated devices depending on the devices they support. Motherboards which have all the ports for connecting various devices on board are known as integrated motherboards. All the latest desktop, server and laptop boards are of the integrated type. Motherboards which do not support connecting devices are known as Non Integrated motherboards. Older boards were of non integrated types.
Classification of Motherboards :
Integrated Motherboards
Integrated motherboards have all the peripheral device slots, input output ports, serial and parallel ports are mounted on the board. The connectors for the various devices such as the hard drive connector and floppy disk drive connector are installed directly on to the motherboard. This arrangement saves a lot of space inside the system. Integrated boards are cheaper in cost as compared to non integrated motherboards. The major disadvantage of these types of motherboards are that if an individual component of the motherboard fails, the whole board may need to be replaced and that can be a costly affair at times.
Non-integrated Motherboards
Non Integrated motherboards have RAM slots integrated on the board. All the input output ports for devices such as the serial and parallel port connectors, other controllers such as connectors for hard drive and floppy disk drives are attached to the system using expansion boards. Expansion boards use more space of the cabinet. If any one of the expansion boards fate, only those particular expansions board needs to be replaced and not the whole board. This type of board is more costly as compared to integrated board as all the devices and ports, and other connectors for the devices need to be installed individually.
The Non integrated Motherboards are almost extinct because these types of motherboards are costly and not very space efficient. Desktop Motherboards Desktop Motherboards is used in personal computers and desktops. As it is used for applications at home and in office, this type of motherboard is the most basic type
Motherboard contains slots, sockets and connectors for connecting various devices. It contains slots for attaching RAM, graphic cards and any other device, and sockets for attaching the microprocessor. It contains a super I/O chip, bus slots for connecting various peripheral devices. A CMOS battery is mounted on the motherboard to keep the system updated with latest date and time. An on board CPU voltage regulator is provided to regulate power supply to the processor. You can configure the motherboard
120 | P a g e using jumpers. Connectors The different connectors on the motherboard enable connection of different devices.
The different connectors on the motherboard are:
• System panel connector (1) Accommodates different front panel system functions such as system power LED, hard disk LED.
• USB headers (2) Functions as connectors for USB module that can provide two additional USB ports, if the USB ports are inadequate.
• Digital audio connector (3) Connects to a module that provides digital sound output, instead of analog
• MDC connector (4) Connects to a modem card module
• Internal audio connectors (5) Enables connection to CD ROM or voice modem card
• GAME/MIDI connector (6) Connects to a GAME/MIDI module that can connect to MIDI devices
• System Management Bus (SMBus) connector (7) Used to connect SMBus devices
• ATX 12V connector (8) Connects to the ATX 12V power supply. The power supply plug will fit these connectors in only one orientation
• ATX Power Connector (9) Connects to the ATX power supply
• CPU and chassis fan connectors (10) Connects to the system cooling fans
• Serial Advanced Technology Attachment (SATA) connectors (11) Connects to the SATA hard disk drives
• IDE connectors (12) Connects to the IDE devices
• Serial port connector (13) Accommodates a second serial port. This connector uses an optional serial port bracket.
• Floppy disk drive connector (14) Connects to the floppy drive through the floppy drive ribbon cable On Board Disk Drive Connectors.
The hard drive, floppy drive and the CD ROM drive is connected to the motherboard using the 3rd disk drive connectors. The primary connector used to connect storage devices such lard drive and the CD ROM drive is the Integrated Development Environment (IDE) port on the motherboard. This is also known as the Parallel Advanced Technology Attachment (PATA). The connector is a normal 40 pin connector.
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A 40 wire connector bus is used to connect the hard drive. Sometimes 80 wire connector bus is also used. The IDE 1 and IDE 2 port on the motherboard is used to connect the hard drive and the CD ROM drive respectively. Serial Advanced Technology Attachment (SATA) technology is used to connect the newer versions of hard drive. SATA technology supports a transfer rate of up to 1.5 Gbps. New SATA II version supports transfer rate of 3 Gbps. SATA data cable is a 7 pin connector.
Form Factor of Motherboard
Form Factor of Motherboard refers to its physical shape, layout and positioning of components on it. It also determines the type of system case it will fit into. Some motherboards that have the same function ability can be packaged into different form factors. The only major difference between such motherboards will be the form factor.
The Motherboard can be classified into three from factors:
1. Obsolete Form Factor
2. Modern Form Factor
3. Proprietary form factor
Obsolete Form Factor
Obsolete form factors consist of Advanced Technology (AT), Baby AT and Low Profile Extended (LPX) form factors. IBM computers used the AT form factor motherboards and the LPX fond factor was mostly used by Western Digital. The size of these motherboards was very large and was used in the earlier days. Nowadays this form factor is not used and is replaced by the ATX and micro ATX form factors.
Baby AT Form Factor
Baby AT Form Factor is very much similar to the original IBM XT motherboard structure. The baby AT form factor fits into most of the system cases. A baby AT motherboard is 8.5 inches wide and about 13 inches long. The length of baby AT motherboards is not fixed. It supports a maximum of 8 slots.
Advanced Technology (AT) Form Factor
AT form factor is also known as the full size AT form factor. This form factor matches the original IBM AT motherboard in structure and layout. This type of motherboard is very large and is about 12 inches wide and 13.8 inches long. The AT form factor is not used much by present day motherboard manufacturers. This type of motherboard does not fit into most of the popular system cases and its size also makes installation and troubleshooting difficult. It supports a maximum of 7 slots.
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Low Profile Extended (LPX) Form Factor
LPX and mini LPX form factors are used for small slim line or low profile cases. This form factor was developed by Western Digital, who no longer produces motherboards. However, many manufacturers have duplicated the LPX form factor. The LPX form factor has advantages like low cost and small size. However, it is difficult to upgrade or expand. These motherboards also exhibit cooling problems and as such the machine shut down automatically at times. It supports a maximum of 8 slots.
Modern Form factor and Proprietary Form Factor will be dealt in details in my next article.
Onboard components of a motherboard
Onboard components of a motherboard include: sockets, ports and jacks. The other ports, sockets and onboard components of the motherboard are: CPU socket (1) Provides place for CPU on the motherboard. This socket is a Zero Insertion Force (ZIF) socket. Northbridge (2) Handles the communication between the CPU, main memory, AGP Port and another very important component known as the south bridge controller. Southbridge (3) Handles all the operations of devices and buses that are not controlled by the north bridge. DDR DIMM sockets (4) Provides support for the memory using DDR DIMM. This motherboard has four DDR DIMM sockets. Super I/O controller (5) Provides the super I/O functionality. Rash ROM (6) Contains programmable BIOS. Standby Power LED (7) Indicates if there is standby power on the motherboard. Audio CODEC (8) Enables audio playback by providing DAC channels. LAN controller (9) Supports networking functions. Mouse port (10) Connects the PS/2 mouse. Parallel port (11) Connects parallel devices like printers. LAN port (12) Enables connection of LAN through a hub. Line In jack (13) Connects audio devices like a tape player. Line Out jack (14) Connects a speaker or a headphone. ,. Microphone jack (15) Connects a microphone. USB ports (16) Enables connection to USB devices. Video port (17) Used to connect to a VGA monitor or another VGA compatible device. Serial port (18) Connects the mouse or other serial devices. Keyboard port (19) Connects the PS 2 keyboard. Memory Slots Memory slots provide an interface for attaching RAM on the board. RAM module is inserted in these slots. Most of the motherboards come equipped with at least 2 memory slots. The maximum number of slots available depends on the motherboard. Memory slots are either Single Inline Memory Module (SIMM) or are Double Inline Memory Module (DIMM). All memory slots are labeled accordingly. SIMM’s need to be inserted in pairs but DIMM may be inserted individually. CPU Socket CPU socket commonly known as CPU slots is an interface that connects the CPU with motherboard. Sockets are mainly used with a particular type of processor. It consists of holes in which the pins of the processor are installed. Sockets are already installed on the board Most of the sockets used are built on the Pin Grid Area (PGA) architecture.
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Processors are placed on to the socket without exerting any pressure. The sockets vary in type and size.
Processor Sockets or Slots
Of course, the motherboard has one or more sockets or slots to hold the processor(s). Single processor motherboards are by far the most common, but dual processor and even quad processor boards are not hard to find. (Quad boards often use special, proprietary designs employing riser cards.) The type of socket or slot used dictates the type of processor (and in some cases the speed) that can be used by the motherboard. Not surprisingly, the standards for processor sockets and slots have been generally defined by Intel. See this discussion of processor sockets and slots, including which support which processors. Most older Intel processors, up to the Pentium Pro, use a square shaped socket for the processor. The newest processors from Intel, starting with the Pentium II, are mounted on a daughterboard, which plugs into an SEC ("single edge connector") slot to connect to the motherboard.
Note: With the invention of the SEC slot for the Pentium II, new motherboards are appearing that use just the one slot for either the Pentium II or the Pentium Pro. Of course the Pentium Pro uses a socket and not a slot, so these manufacturers create a daughterboard similar to the Pentium II's, that just contains a socket for the Pentium Pro chip. This gives great flexibility since either chip can then be used with the same motherboard.
Most modern motherboards that have a socket use the ZIF (zero insertion force) style socket, that allows the processor to be inserted or removed from the motherboard by using a lever that tightens or loosens the processor's pins in the socket. This is a vast improvement over the older style sockets, which required you to exert considerable force on the surface of a delicate (and expensive) processor, just to get it into the motherboard. (Getting it out was of course even harder!)
Memory Sockets
Most motherboards today come with between 2 and 8 sockets for the insertion of memory. These are usually either SIMMs (single inline memory modules) or DIMMs (dual inline memory modules). These can come in different sizes. See here for details on memory packaging technologies.
The motherboard usually labels these sockets "SIMM0" through "SIMM7" or "DIMM1" through "DIMM3", etc. The sockets are almost always filled starting with the lowest numbered socket first. Most Pentium class or higher motherboards require SIMMs to be inserted in pairs, but DIMMs may be inserted individually. See here for details on memory bank size and selecting appropriate memory.
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Note: The maximum number of memory modules on a motherboard is dictated by the design of the motherboard's chipset. However, not all motherboards have the maximum number of sockets that the chipset allows for, so you need to shop around if memory expansion is an important issue to you.
Expansion slot
Alternatively referred to as an expansion port , an expansion slot is a slot located inside a computer on the motherboard or riser board that allows additional boards to be connected to it. Below is a listing of some of the expansion slots commonly found in IBM compatible computers as well as other brands of computers and a graphic illustration of a motherboard and its expansion slots.
IDE Connector
Short for Integrated Drive Electronics or IBM Disc Electronics, IDE is more commonly known as ATA or Parallel ATA (PATA) and is a standard interface for IBM compatible hard drives. IDE is different from the Small Computer Systems Interface (SCSI ) and Enhanced Small Device Interface (ESDI) because its controllers are on each drive, meaning the drive can connect directly to the motherboard or controller. IDE and its updated successor, Enhanced IDE (EIDE), are the most common drive interfaces found in IBM compatible computers today. Below is a picture of the actual IDE connector on the back of a hard disk drive, a picture of what an IDE cable looks like, and the IDE channels it connects to on the motherboard.
FDD connector
FDD connector it is similar in function to the IDE connector. It is a 34 pin ribbon connector that carries data between the motherboard and any floppy drive installed in the PC. Not accessible with PC cover on.
COM port redirector
A COM port redirector is specialized software (often including device driver and user application) that includes the underlying network software necessary to access networked device servers that provide remote serial devices or modems.
Parallel port
A parallel port is a type of interface found on computers (personal and otherwise) for connecting various peripherals. In computing, a parallel port is a parallel communication physical interface. It is also known as a printer port or Centronics port . The IEEE
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1284 standard defines the bi directional version of the port, which allows the transmission and reception of data bits at the same time.
Uses
Before the advent of USB , the parallel interface was adapted to access a number of peripheral devices other than printers. Probably one of the earliest devices to use parallel were dongles used as a hardware key form of software copy protection. Zip drives and scanners were early implementations followed by external modems , sound cards, webcams, gamepads , joysticks, external hard disk drives and CD ROM drives. Adapters were available to run SCSI devices via parallel. Other devices such as EPROM programmers and hardware controllers could be connected via the parallel port.
USB
Universal Serial Bus (USB ) is an industry standard developed in the mid 1990s that defines the cables, connectors and communications protocols used in a bus for connection, communication and power supply between computers and electronic devices.[1]
USB was designed to standardize the connection of computer peripherals , such as keyboards, pointing devices , digital cameras, printers, portable media players , disk drives and network adapters to personal computers , both to communicate and to supply electric power . It has become commonplace on other devices, such as smartphones, PDAs and video game consoles . USB has effectively replaced a variety of earlier interfaces, such as serial and parallel ports, as well as separate power chargers for portable devices.
BIOS
In IBM PC compatible computers, the basic input/output system (BIOS) , also known as the System BIOS or ROM BIOS ( /ˈbaɪ.oʊs/), is a de facto standard defining a firmware interface. [1] The name originated in earlier computers running CP/M and other operating systems, where the BIOS was loaded from disc rather than stored as firmware (EPROMs were not yet available); and from aro und 2010 the BIOS firmware of PCs started to be replaced by a Unified Extensible Firmware Interface (UEFI).
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Phoenix AwardBIOS CMOS (non volatile memory) Setup utility on a standard PC
The BIOS software is built into the PC , and is the first code run by a PC when powered on ('boot firmware'). When the PC starts up, the first job for the BIOS is to initialize and identify system devices such as the video display card, keyboard and mouse , hard disk drive, optical disc drive and other hardware . The BIOS then locates boot loader software held on a peripheral device (designated as a 'boot device'), such as a hard disk or a CD/DVD , and loads and executes that software, giving it control of the PC. [2] This process is known as booting , or booting up, which is short for bootstrapping .
BIOS software is stored on a non volatile ROM chip on the motherboard . It is specifically designed to work with each particular model of computer, interfacing with various devices that make up the complementary chipset of the system. In modern computer systems the BIOS chip's contents can be rewritten without removing it from the motherbo ard, allowing BIOS software to be upgraded in place.
A BIOS has a user interface (UI), typically a menu system accessed by pressing a certain key on the keyboard when the PC star ts. In the BIOS UI, a user can:
• configure hardware
• set the system clock
• enable or disable system components
• select which devices are eligible to be a potential boot device
• set variou s password prompts, such as a password for securing access to the BIOS UI functions itself and preventing malicious users from booting the system from unauthorized peripheral devices.
The BIOS provides a small library of basic input/output functions used to operate and control the peripherals such as the keyboard, text display functions and so forth, and these software library functions are callable by external softw are. In the IBM PC and AT, certain peripheral cards such as hard drive controllers and video display adapters
127 | P a g e carried their own BIOS extension Option ROM, which provided additional functionality. Operating systems and executive software, designed to supersede this basic firmware functionality, will provide replacement software interfaces to applications.
The role of the BIOS has changed over time. As of 2011, the BIOS is being replaced by the more complex Extensible Firmware Interface (EFI) in many new machines, but BIOS remains in widespread use, and EFI booting has only been supported in Microsoft's operating system products supporting GPT [3] and Linux kernels 2.6.1 and greater builds (and in Mac OS X on Intel based Macs). [4] However, the distinction between BIOS and EFI is rarely made in terminology by the average computer user, making BIOS a catch all term for both systems.
Front panel connector
One somewhat tedious but vital step in assembling your homebuilt computer is to connect all those little wires for the front panel switches and LED's from the case to the motherboard.
If you purchased a "barebones" computer with the motherboard already mounted, then this was probably done for you already. Otherwise, you'll have to do it yourself. Hopefully, you have good eyes and can read the tiny lettering on both the connectors and the motherboard. Otherwise, break out the bifocals!
Each switch and LED on the front panel has a connector attached to it that must be connected to the appropriate pins on the motherboard.
Some of the connectors (especially the LED's) are polarized, meaning that they have to be connected in the correct polarity. Polarized connectors have a little arrow or a plus sign by the positive wire, but no keyway to prevent you from attaching them backwards.
Long story short: If one of your LED's doesn't work (or if it stays lit all the time), chances are that you attached it backwards. If so, simply correct it.
Unfortunately, there's no universal rule about the positions of these pins. To determine the correct pins to attach the connectors to, you will have to consult the motherboard manual or look for the teensy lettering on the motherboard adjacent to the pins.
The basic front panel headers found on most motherboards are those for the PC speaker (the one built into most cases that beeps when the computer passes POST),
128 | P a g e the power switch, the reset switch, the hard drive activity LED, the power LED, and sometimes a few others. Of these, the leads for the LEDs must be connected in the proper polarity in order to work properly. The rest should be connected in the proper polarity just for the sake of doing things professionally, but they will work even if they're attached backwards.
Time to Double-Check
Before firing up your new computer, take a few moments to double check the following items:
• Check all the fans to make sure they are properly connected. Starting up your computer with the CPU fan disconnected will likely kill your processor!
• Make sure that all wires and cables are safely tied away from the fans. Neatness counts. Use plastic cable ties, not metal twist ties. If you can't get plastic cable ties, then use electrical tape.
• Check that all of the power and data cables are securely connected and are attached in the correct polarity.
• Make sure that there are no tools, screws, or jumpers floating around in the case.
• Check that all expansion cards and RAM modules are securely seated Display connector
What is DVI?
DVI stands for Digital Video Interface, a digital interface developed by a consortium of computer industry leaders called the Digital Display Working Group (DDWG). It was designed to provide an industry standard digital connection between a personal computer and a desktop display.
What are the advantages of DVI?
Traditional CRT (Cathode Ray Tube) displays use an analogue signal to receive image data from the computers graphics card. For this reason, early graphics cards needed to convert their native digital signal into analogue in order to support CRT monitors.
LCD monitors are digital display devices, but when they were first introduced they needed to be able to accept and adapt this analogue signal to ensure compatibility with
129 | P a g e the majority of available computers. In order for the LCD to accept the computer's analogue output, the signal had to be reconverted to digital.
Since both the computer and the LCD digital monitor accept and transmit digital signals, the process of translating digital to analogue is fundamentally unnecessary. The DVI digital connection removes this digital – analogue – digital conversion process, and so removes inaccuracies and information loss due to each conversion process.
DVI, being a digital interface suffers none of the problems traditionally associated with analogue interfaces, such as noise, “sparkles”, “ghosting”, “snow”, poor colour matching and “softness” caused by loss of sharpness.
The DVI interface has proven to be extremely versatile; its two connectors provide manufacturers with the flexibility to support digital devices while remaining backwards compatible with analogue devices.
DVI Connection Types
To provide backwards compatibility with analogue displays. The DDWG specified that the DVI connector should accommodate both analogue and digital interfaces; this is implemented in the DVI I (DVI Integrated) connector. A different connector DVI D (DVI Digital) is also specified and this handles digital only signals.
DVI-Integrated (DVI-I) supports both digital and analogue connections to the display. The DVI-I interface connector carries single
or dual-link digital signals on 24 pins and uses 5 pins to carry the analogue connection. It is easily distinguishable by the cross shaped slot on the right of the connector. (Picture shows female DVI-I connector end view).
DVI-Digital (DVI-D) supports digital only connections. Only DVI-D cables can be attached to this Female connector on a monitor. DVI-I cables will not fit! This interface is designed for a 12 or 24 pin connection to enable single or dual-link mode activation. (Picture shows female DVI-D connector end view).
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DVI Analogue Connections & Adaptors
Our DVI Cables support even the highest defined digital monitor resolutions (Dual Link Digital), but they do not support analogue RGB signals. If an analogue connection is needed, we recommend using the DVI I to VGA Short Adaptor Cable (Part No. 41222) in conjunction with high quality VGA Cables. This is an economical and high quality solution and also does not impose the distance limitation of 7.5m for DVI cable lengths.
Our DVI / DFP adaptors can connect older DFP type monitors and graphics cards with current DVI models. Adaptors are available as DVI Male to DFP Female (Part No. 41220) and DFP Male to DVI Female (Part No. 41221).
Adaptors are also available to connect your Apple computer with ADC output to a digital display with DVI input ADC to DVI Adaptor Cable (Part No. 41224).
DVI Cables with RF-BLOK
In keeping with the LINDY tradition of premium quality computer connection technology, LINDY DVI Cables use a rugged construction RF BLOK shielded design, ensuring optimum performance from your flat panel monitor. LINDY RF BLOK cables use a one piece metal block EMI/RF shield that gives reduced interference, and increased insulation resistance of up to 25%. The innovative interconnect design means there is no soldering required in the assembly of the cable. The design and excellent RF shielding also means that there is no requirement for a ferrite core, so the cable is less stressed and more flexible & ndash; an advantage when the cabl e needs to be bent in tight spaces.
LINDY DVI-D cables can be used with any digital flat panel display, and with any DVI graphics card! LINDY extension cables (Dual Link Digital) use the Female connector with integrated Micro-Cross connector
Up To 10 Metres Distance Between Digital Monitor & Computer
With our DVI cables you can extend the distance for digital monitors with fixed cables and socket connectors up to a distance of 10m. Please note that cable lengths over 7.5m are above the recommended length laid down by the DDWG. This factor also
131 | P a g e depends on the hardware combination of graphics card and monitor as to how far this distance can be exceeded.
Please also remember that every additional plug socket connection you make lowers the quality of the signal transmission. Therefore, especially at larger distances always try to use a single connection cable if possible. At distances over 5m typical problems with digital connections show up as the loss of one color (Red or Green or Blue), poor picture quality and finally a complete loss of synchronization.
Keyboard Connector
The keyboard connector is the device at the end of the cable that is used to attach the keyboard to the system . There are two standard types of connectors, which represent the only connector types ever used in the PC world, if you ignore special proprietary hardware. At least, these were the only connector types used until USB became a popular interface. :^)
Well, let's look at regular connectors first. The older style is the larger of the two, called the 5-pin DIN keyboard connector. It was used on the first PCs, and became the standard connection through about the mid 1990s. The smaller is the 6 pin, so called "mini DIN" keyboard connector. ( DIN stands for Deutsche Industrie Norm , a German standards setting organization. DIN't you always want to know that? ;^) ) The smaller connector was introduced on the IBM model PS/2 and is therefore sometimes called a "PS/2 connector". It has replaced the larger connector as the standard for modern PCs.
Note: The 5-pin DIN connector is sometimes called the "AT" style for the older IBM model, and the 6-pin "mini-DIN" a "PS/2" style connector, again after the IBM model that popularized it.
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A 5 pin DIN keyboard connector (left) and a 6 pin mini DIN keyboard connector (right). Note the block in the middle of the mini DIN, used for keying.
The signal assignments for each connector can be found in this table:
Pin # 5-pin DIN Connector 6-pin "mini-DIN" Connector
1 Keyboard Clock Keyboard Data
2 Keyboard Data (not connected)
3 (not connected) Ground
4 Ground Power (+5V)
5 Power (+5V) Keyboard Clock
6 (not connected)
(Refer to the diagram to see the pin number assignments for each connector. For more information on the signals themselves, see this page on signaling .
You'll notice a few things about the table. First, there are only four actual signals used in the standard keyboard interface; the extra pins on both types of connector are not used. (This mismatch means that the connectors were chosen either from existing designs to save development costs, or that room was left for future expansion that was never used.
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Both occur commonly in the PC industry.) Also, the signals are the same for the two types of connector they just use different pins. This means that simple mechanical adapters can be made to convert between the two. These adapters let a keyboard that terminates in a large connector work on a system that requires a small connector, and vice versa. See here for more .
Failure of keyboard connectors is quite rare; they are rather solid and problems are unusual. Occasionally a loose connection will develop within the connector, however. The bigger concern is that sometimes the connector can be hard to insert into the matching connector on the motherboard. Some "persuasion" may be necessary, but if you use too much force you can damage the connector on the motherboard, which usually cannot be repaired the board itself must be replaced. The connector on the motherboard "stands up" from the surface of the board, making it rather fragile. (I have actually seen someone wreck a motherboard this way!)
As you can see from the illustrations, these connectors are intentionally asymmetric, to prevent mismatching the pins. The connectors are marked with an arrow on the top of the connector, to help you align the connector to its mate on the motherboard. Of course, if you don't align the connector properly and try to force it in, thinking it is just "stuck", you are likely to be unhappy with the result... so look for that arrow. :^)
In the last couple of years, a new keyboard interface has arrived on the market, which connects to the system using the universal serial bus (USB). These of course use standard USB connectors, which are completely different from regular keyboard connectors, and USB signaling and protocols. See the discussions of interfacing and signaling for more
Drive Power Connectors
The power supply provides power to internal hard disk, floppy disk, CD/DVD and other drives directly, through four wire connectors that are designed to attach to the rear of each drive. The four wires provide +5 V and +12 V power, along with two grounds, to the various drives that use them.
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Schematic diagram of a large style hard disk drive cableconnector (the small style is wired the same, the shape and size are just different, as shown below. The wires used for these connectors vary widely from system to system. For the larger style connector, AWG 16 to 18 are common. For the smaller size, AWG 18 down to AWG 22 are sometimes specified (since floppies draw little current).
The connectors themselves come in two basic styles. The larger size, often called a Molex connector (after the name of one of the big connector companies) is keyed by virtue of the connector itself being "D shaped", and is used on most internal drives, including hard disk, CD/DVD, Zip and other removable media drives, and the older 5.25" floppy disk drives. The smaller size, typically called a "mini plug", is used for the newer style of 3.5" floppies. It is also keyed, but in a different way than the larger connector, and actually secures to its mating connector with a retention clip of sorts.
Large and small disk drive connectors. The tab in the middle bottom of the small connector (not shown) fits into a retention clip on the floppy disk drive and holds it in place. The large connectors secure simply by friction (which can be a lot stronger than it sounds like, believe me!)
The number of connectors that come with each power supply varies considerably. In general, the bigger the supply, the more devices the manufacturer expects you to run, so the more connectors are included. Totals can range from 3 or 4 connectors to as many as a dozen. Another factor is just general quality; some makers skimp on the connectors to save money, and make you buy adapters to let you run additional drives. These adapters, usually called "Y splitters" or "Y cables" after their general shape (sort of :^) ) contain one male and two female large style hard disk connectors, cost around $2 5 in the U.S,. and are available in most electronics or computer stores. They are increasingly needed in modern systems, because not only do newer systems have more drives, they also have more fans and cooling devices, which also often attach using a disk drive power connector. Do remember, however, that adding a Y splitter
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Warning: It is best to avoid Y splitters if possible, for a few reasons. First, there have been reports of incorrectly wired Y splitters. Watch out for them, as they have the potential to damage your equipment. (It's pretty easy to see if the adapter has been wired correctly by inspecting it carefully. Using an ohmmeter to test for correct connectivity is even better.) Second, they are an additional potential source of failure in the system, and are often cheaply made and hard to align and plug in properly. Third, they can further clutter the inside of a busy case. Fourth, every time you share two devices on a single connector, all the power drawn by the two devices has to travel down the same set of wires from the power supply. If you chain three or four drives off the same connector using multiple splitters you may exceed the current rating for the wires and/or connector. See the discussion of wire size and resistance in the section on the motherboard connectors for more details.
A Y splitter cable for running two drives off a single large hard disk cable connector .
Most systems only come with a single mini plug connector because most systems come with only a single floppy drive that uses it but some may come with two. If you need an additional mini plug connector in a system with only one, or if the first one breaks, you can employ a simple adapter to change a large style into a small style. (They may make them the other way as well, but I am not sure.) You may also on occasion see mini plugs, or mini plug adapters, that only use two wires instead of the standard four. They omit pins 1 and 2 because newer floppies may use only the +5 voltage. This won't cause problems in most cases, but beware.
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An adapter to change a large style drive power connector into a small style connector.
A couple of final thoughts. The power supply fan in your PC runs directly off a connection within the supply itself, but additional fans within the case are growing in popularity, and typically each of these requires a drive connector. They don't draw very much power (but fancier electrothermal coolers can draw quite a bit). Finally, the hot swappable drives used with RAID in newer server boxes typically do not use standard drive connectors for their drives. They make use of a technology called single connector attachment (SCA) . In this scheme, special bays are installed in the system, which take either standard power connectors from the power supply, or a special wiring harness. The drives themselves plug into the bays and draw all their power and signals from a single mated connector, one half on the back of the drive and one half inside the bay. This allows them to be easily removed while the system is still operating.
Sound Port
Port Audio is a computer library for audio playback and recording. Its primary goal is to be a cross platform, open source library, so that programs that use it can run on many different computer operating systems. Like many other libraries, especially those whose primary goal is portability, Port Audio is written in the C programming language.
Port Audio is part of the Port Music project, which aims to provide a set of platform independent libraries for music software. The free audio editor Audacity uses the Port Audio library, and so does the JACK Audio Connection Kit on the Windows platform.
Port Audio is based on a callback paradigm, similar to JACK and ASIO.
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PS/2 connector
The PS/2 connector is a 6 pin Mini DIN connector used for connecting some keyboards and mice to a PC compatible computer system. Its name comes from the IBM Personal System/2 series of personal computers, with which it was introduced in 1987. The PS/2 mouse connector generally replaced the older DE 9 RS 232 "serial mouse" connector, while the PS/2 keyboard connector replaced the larger 5 pin/180° DIN connector used in the IBM PC/AT design. The PS/2 designs on keyboard and mouse interfaces are electrically similar and employ the same communication protocol. However, a given system's keyboard and mouse port may not be interchangeable since the two devices use a different set of commands
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