computer hardware

A personal is made up of multiple physical components of computer hardware, upon which can be installed a system software called operating system and a multitude of software applications to perform the operator's desired functions.

Though a PC comes in many different forms, a typical personal computer consists of a case or chassis in a tower shape (desktop), containing components such as a motherboard.

Motherboard Main article: Motherboard

The motherboard is the main component inside the case. It is a large rectangular board with integrated circuitry that connects the rest of the parts of the computer including the CPU, the RAM, the disk drives (CD, DVD, hard disk, or any others) as well as any peripherals connected via the ports or the expansion slots.

Components directly attached to the motherboard include:

y The central processing unit (CPU) performs most of the calculations which enable a computer to function, and is sometimes referred to as the "brain" of the computer. It is usually cooled by a heat sink and fan. y The chip set mediates communication between the CPU and the other components of the system, including main memory. y RAM (Random Access Memory) stores resident part of the current running OS (OS core and so on) and all running processes (applications parts, using CPU or input/output (I/O) channels or waiting for CPU or I/O channels). y The BIOS includes boot firmware and power management. The Basic Input Output System tasks are handled by operating system drivers. y Internal Buses connect the CPU to various internal components and to expansion cards for graphics and sound. o Current  The north bridge memory controller, for RAM and PCI Express  PCI Express, for expansion cards such as graphics and physics processors, and high-end network interfaces  PCI, for other expansion cards  SATA, for disk drives o Obsolete  ATA (superseded by SATA)  AGP (superseded by PCI Express)  VLB VESA Local Bus (superseded by AGP)  ISA (expansion card slot format obsolete in PCs, but still used in industrial ) y External Bus Controllers support ports for external peripherals. These ports may be controlled directly by the south bridge I/O controller or based on expansion cards attached to the motherboard through the PCI bus.

y USB y FireWire y eSATA y SCSI

Power supply A power supply unit (PSU) converts alternating current (AC) electric power to low-voltage DC power for the internal components of the computer. Some power supplies have a switch to change between 230 V and 115 V. Other models have automatic sensors that switch input voltage automatically, or are able to accept any voltage between those limits. Power supply units used in computers are nearly always switch mode power supplies (SMPS). The SMPS provides regulated direct current power at the several voltages required by the motherboard and accessories such as disk drives and cooling fans.

Removable media devices

y CD (compact disc) - the most common type of removable media, suitable for music and data. o CD-ROM Drive - a device used for reading data from a CD. o CD Writer - a device used for both reading and writing data to and from a CD. y DVD (digital versatile disc) - a popular type of removable media that is the same dimensions as a CD but stores up to 12 times as much information. It is the most common way of transferring digital video, and is popular for data storage. o DVD-ROM Drive - a device used for reading data from a DVD. o DVD Writer - a device used for both reading and writing data to and from a DVD. o DVD-RAM Drive - a device used for rapid writing and reading of data from a special type of DVD. y Blu-ray Disc - a high-density optical disc format for data and high-definition video. Can store 70 times as much information as a CD. o BD-ROM Drive - a device used for reading data from a Blu-ray disc. o BD Writer - a device used for both reading and writing data to and from a Blu-ray disc. y HD DVD - a discontinued competitor to the Blu-ray format. y Floppy disk - an outdated storage device consisting of a thin disk of a flexible magnetic storage medium. Used today mainly for loading RAID drivers. y Iomega Zip drive - an outdated medium-capacity removable disk storage system, first introduced by Iomega in 1994. y USB flash drive - a flash memory data storage device integrated with a USB interface, typically small, lightweight, removable, and rewritable. Capacities vary, from hundreds of megabytes (in the same ballpark as CDs) to tens of gigabytes (surpassing, at great expense, Blu-ray discs). y Tape drive - a device that reads and writes data on a magnetic tape, used for long term storage and backups.

Secondary storage

Hardware that keeps data inside the computer for later use and remains persistent even when the computer has no power. y Hard disk - for medium-term storage of data. y Solid-state drive - a device similar to hard disk, but containing no moving parts and stores data in a digital format. y RAID array controller - a device to manage several internal or external hard disks and optionally some peripherals in order to achieve performance or reliability improvement in what is called a RAID array.

Sound card Enables the computer to output sound to audio devices, as well as accept input from a microphone. Most modern computers have sound cards built-in to the motherboard, though it is common for a user to install a separate sound card as an upgrade. Most sound cards, either built-in or added, have surround sound capabilities.

Input and output peripherals Input and output devices are typically housed externally to the main computer chassis. The following are either standard or very common to many computer systems.

Input Main article: Input device

y Text input devices o Keyboard - a device to input text and characters by depressing buttons (referred to as keys or buttons). y Pointing devices o Mouse - a pointing device that detects two dimensional motion relative to its supporting surface.  Optical Mouse - uses light to determine mouse motion. o Trackball - a pointing device consisting of an exposed protruding ball housed in a socket that detects rotation about two axes. o Touchscreen - senses the user pressing directly on the display

y Gaming devices o Joystick - a control device that consists of a handheld stick that pivots around one end, to detect angles in two or three dimensions. o Game pad - a hand held game controller that relies on the digits (especially thumbs) to provide input. o Game controller - a specific type of controller specialized for certain gaming purposes. y Image, Video input devices o Image scanner - a device that provides input by analyzing images, printed text, handwriting, or an object. o Web cam - a video camera used to provide visual input that can be easily transferred over the . y Audio input devices o Microphone - an acoustic sensor that provides input by converting sound into electrical signals.

Output Main article: Output device

y Printer - a device that produces a permanent human-readable text of graphic document. y Speakers - typically a pair of devices (2 channels) which convert electrical signals into audio. o Headphones - for a single user hearing the audio. y Monitor - an electronic visual display with textual and graphical information from the computer. o CRT - (Cathode Ray Tube) display o LCD - (Liquid Crystal Display) as of 2010, it is the primary visual display for personal computers. o LED - (light-emitting diode) display o OLED - Organic Light-Emitting Diode

what are computers used for?

Computers are used for a wide variety of purposes.

Data processing is commercial and financial work. This includes such things as billing, shipping and receiving, inventory control, and similar business related functions, as well as the ³electronic office´.

Scientific processing is using a computer to support science. This can be as simple as gathering and analyzing raw data and as complex as modelling natural phenomenon (weather and climate models, thermodynamics, nuclear engineering, etc.).

Multimedia includes content creation (composing music, performing music, recording music, editing film and video, special effects, animation, illustration, laying out print materials, etc.) and multimedia playback (games, DVDs, instructional materials, etc.).

parts of a computer

The classic crude oversimplication of a computer is that it contains three elements: processor unit, memory, and I/O (input/output). The borders between those three terms are highly ambigious, non-contiguous, and erratically shifting. BIOS

(bī ōs) Acronym for basic input/output system, the built-in software that determines what a computer can do without accessing programs from a disk. On PCs, the BIOS contains all the code required to control the keyboard, display screen, disk drives, serial communications, and a number of miscellaneous functions.

The BIOS is typically placed in a ROM chip that comes with the computer (it is often called a ROM BIOS). This ensures that the BIOS will always be available and will not be damaged by disk failures. It also makes it possible for a computer to boot itself. Because RAM is faster than ROM, though, many computer manufacturers design systems so that the BIOS is copied from ROM to RAM each time the computer is booted. This is known as shadowing.

Many modern PCs have a flash BIOS, which means that the BIOS has been recorded on a flash memory chip, which can be updated if necessary.

The PC BIOS is fairly standardized, so all PCs are similar at this level (although there are different BIOS versions). Additional DOS functions are usually added through software modules. This means you can upgrade to a newer version of DOS without changing the BIOS.

PC BIOSes that can handle Plug-and-Play (PnP) devices are known as PnP BIOSes, or PnP- aware BIOSes. These BIOSes are always implemented with flash memory rather than ROM.

Bios is an important part of the computer or to be specific an important part of the system unit. It is the one that checks if some of your hardware components are workng properly. But in making a setup in the BIOs you should have to be careful in configuring a BIOS, because if you cant able to configure it well it can cause a damage in your motherboard and possible to happen your motherboard will not function anymore. And especially you have also to protect it in other of your computer. You can make a password to protect you BIOS from other user. In you can see that there is set supervisor password or set password, in which you can able to protect your BIOS by enabling it. BIOS

The BIOS software is built into the PC, and is the first code run by a PC when powered on ('boot firmware'). The primary function of the BIOS is to load and start an operating system. 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, CD/DVD drive and other hardware. The BIOS then locates software held on a peripheral device (designated as a 'boot device'), such as a hard disk or a CD, 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 built into the system on the mother board. The BIOS software is specifically designed to work with the particular type of system in question, including having a knowledge of the workings of various devices that make up the complementary chipset of the system. In modern computer systems, the BIOS chip's contents can be rewritten allowing BIOS software to be upgraded.

A BIOS will also have a user interface (or UI for short). Typically this is a menu system accessed by pressing a certain key on the keyboard when the PC starts. In the BIOS UI, a user can:

y configure hardware y set the system clock y enable or disable system components y select which devices are eligible to be a potential boot device y set various 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 software. In the IBM PC and AT, certain peripheral cards such as hard-drive controllers and video display adapters carried their own BIOS extension 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; today BIOS is a legacy system, superseded by the more complex EFI (EFI), but BIOS remains in widespread use, and EFI booting has only been supported in Microsoft OS products supporting GPT [3] and Linux Kernels 2.6.1 and greater builds [4] BIOS is primarily associated with the 16-bit, 32-bit, and the beginning of the 64-bit architecture eras, while EFI is used for some newer 32-bit and 64-bit architectures. Today BIOS is primarily used for booting a system and for video initialization (in X.org); but otherwise is not used during the ordinary running of a system, while in early systems (particularly in the 16-bit era), BIOS was used for hardware access ± operating systems (notably MS-DOS) would call the BIOS rather than directly accessing the hardware. In the 32-bit era and later, operating systems instead generally directly accessed the hardware using their own device drivers. 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.

Terminology

The term first appeared in the CP/M operating system, describing the part of CP/M loaded during boot time that interfaced directly with the hardware (CP/M machines usually had only a simple boot loader in their ROM). Most versions of DOS have a file called "IBMBIO.COM" or "IO.SYS" that is analogous to the CP/M BIOS.

Among other classes of computers, the generic terms boot monitor, boot loader or boot ROM were commonly used. Some Sun and PowerPC-based computers use Open Firmware for this purpose. There are a few alternatives for Legacy BIOS in the x86 world: Extensible Firmware Interface, Open Firmware (used on the OLPC XO-1) and coreboot.

IBM PC-compatible BIOS chips

In principle, the BIOS in ROM was customized to the particular manufacturer's hardware, allowing low- level services (such as reading a keystroke or writing a sector of data to diskette) to be provided in a standardized way to the operating system. For example, an IBM PC might have had either a monochrome or a color display adapter, using different display memory addresses and hardware - but the BIOS service to print a character on the screen in text mode would be the same.

Prior to the early 1990s, BIOSes were stored in ROM or PROM chips, which could not be altered by users. As its complexity and need for updates grew, and re-programmable parts became more available, BIOS firmware was most commonly stored on EEPROM or flash memory devices. According to Robert Braver, the president of the BIOS manufacturer Micro Firmware, Flash BIOS chips became common around 1995 because the electrically erasable PROM (EEPROM) chips are cheaper and easier to program than standard erasable PROM (EPROM) chips. EPROM chips may be erased by prolonged exposure to ultraviolet light, which accessed the chip via the window. Chip manufacturers use EPROM programmers (blasters) to program EPROM chips. Electrically erasable (EEPROM) chips come with the additional feature of allowing a BIOS reprogramming via higher-than-normal amounts of voltage.[5] BIOS versions are upgraded to take advantage of newer versions of hardware and to correct bugs in previous revisions of BIOSes.[6]

Flashing the BIOS

In modern PCs the BIOS is stored in rewritable memory, allowing the contents to be replaced or 'rewritten'. This rewriting of the contents is sometimes termed 'flashing'. This is done by a special program, usually provided by the system's manufacturer. A file containing such contents is sometimes termed 'a BIOS image'. A BIOS might be reflashed in order to upgrade to a newer version to fix bugs or provide improved performance or to support newer hardware, or a reflashing operation might be needed to fix a damaged BIOS.

Overclocking

Some BIOS chips allow overclocking, an action in which the CPU is adjusted to a higher clock rate than its factory preset. Overclocking may, however, seriously compromise system reliability in insufficiently cooled computers and generally shorten component lifespan.

Virus attacks

There are at least three known BIOS attack viruses, two of which were for demonstration purposes.

CIH

The first was a virus which was able to erase Flash ROM BIOS content, rendering computer systems unstable. CIH, also known as "Chernobyl Virus", appeared for the first time in mid-1998 and became active in April 1999. It affected systems' BIOS's and often they could not be fixed on their own since they were no longer able to boot at all. To repair this, Flash ROM IC had to be removed from the motherboard to be reprogrammed elsewhere. Damage from CIH was possible since the virus was specifically targeted at the then widespread i430TX motherboard chipset, and the most common operating systems of the time were based on the Windows 9x family allowing direct hardware access to all programs.

Modern systems are not vulnerable to CIH because of a variety of chipsets being used which are incompatible with the Intel i430TX chipset, and also other Flash ROM IC types. There is also extra protection from accidental BIOS rewrites in the form of boot blocks which are protected from accidental overwrite or dual and quad BIOS equipped systems which may, in the event of a crash, use a backup BIOS. Also, all modern operating systems like Linux, Mac OS X, Windows NT-based Windows OS like Windows 2000, Windows XP and newer, do not allow user mode programs to have direct hardware access. As a result, as of 2008, CIH has become essentially harmless, at worst causing annoyance by infecting executable files and triggering alerts from antivirus software. Other BIOS viruses remain possible, however[8]: since most Windows users run all applications with administrative privileges, a modern CIH-like virus could in principle still gain access to hardware.

Firmware on adapter cards

A computer system can contain several BIOS firmware chips. The motherboard BIOS typically contains code to access hardware components absolutely necessary for bootstrapping the system, such as the keyboard (either PS/2 or on a USB human interface device), and storage (floppy drives, if available, and IDE or SATA hard disk controllers). In addition, plug-in adapter cards such as SCSI, RAID, Network interface cards, and video boards often include their own BIOS (e.g. Video BIOS), complementing or replacing the system BIOS code for the given component. (This code is generally referred to as an option ROM.) Even devices built into the motherboard can behave in this way; their option ROMs can be stored as separate code on the main BIOS flash chip, and upgraded either in tandem with, or separately to, the main BIOS.

An add-in card usually only requires an option ROM if it:

y Needs to be used before the operating system can be loaded (usually this means it is required in the bootstrapping process), and y Is too sophisticated or specific a device to be handled by the main BIOS

Older PC operating systems, such as MS-DOS (including all DOS-based versions of ), and early-stage bootloaders, may continue to use the BIOS for input and output. However, the restrictions of the BIOS environment means that modern OSes will almost always use their own device drivers to directly control the hardware. Generally, these device drivers only use BIOS and option ROM calls for very specific (non-performance-critical) tasks, such as preliminary device initialization.

In order to discover memory-mapped ISA option ROMs during the boot process, PC BIOS implementations scan real memory from 0xC0000 to 0xF0000 on 2 KiB boundaries, looking for a ROM signature: 0xAA55 (0x55 followed by 0xAA, since the x86 architecture is little-endian). In a valid expansion ROM, this signature is immediately followed by a single byte indicating the number of 512-byte blocks it occupies in real memory. The next byte contains an offset describing the option ROM's entry point, to which the BIOS immediately transfers control. At this point, the expansion ROM code takes over, using BIOS services to register interrupt vectors for use by post-boot applications, provide a user configuration interface, or display diagnostic information.

There are many methods and utilities for examining the contents of various motherboard BIOS and expansion ROMs, such as Microsoft DEBUG or the UNIX dd.

Changing role of the BIOS

Some operating systems, for example MS-DOS, rely on the BIOS to carry out most input/output tasks within the PC.[11] A variety of technical reasons makes it inefficient for some recent operating systems written for 32-bit CPUs such as Linux and Microsoft Windows to invoke the BIOS directly. Larger, more powerful, servers and workstations using PowerPC or SPARC CPUs by several manufacturers developed a platform-independent Open Firmware (IEEE-1275), based on the Forth programming language. It is included with Sun's SPARC computers, IBM's RS/6000 line, and other PowerPC CHRP motherboards. Later x86-based personal computer operating systems, like Windows NT, use their own, native drivers which also makes it much easier to extend support to new hardware, while the BIOS still relies on a legacy 16-bit real mode runtime interface.

There was a similar transition for the Apple Macintosh, where the system software originally relied heavily on the ToolBox²a set of drivers and other useful routines stored in ROM based on Motorola's 680x0 CPUs. These Apple ROMs were replaced by Open Firmware in the PowerPC Macintosh, then EFI in Intel Macintosh computers.

Later BIOS took on more complex functions, by way of interfaces such as ACPI; these functions include power management, hot swapping, thermal management. However BIOS limitations (16- bit processor mode, only 1 MiB addressable space, PC AT hardware dependencies, etc.) were seen as clearly unacceptable for the newer computer platforms. Extensible Firmware Interface (EFI) is a specification which replaces the runtime interface of the legacy BIOS. Initially written for the Itanium architecture, EFI is now available for x86 and x86-64 platforms; the specification development is driven by The Unified EFI Forum, an industry Special Interest Group.

Linux has supported EFI via the elilo boot loader. The Open Source community increased their effort to develop a replacement for proprietary BIOSes and their future incarnations with an open sourced counterpart through the coreboot and OpenBIOS/Open Firmware projects. AMD provided product specifications for some chipsets, and Google is sponsoring the project. Motherboard manufacturer Tyan offers coreboot next to the standard BIOS with their Opteron line of motherboards. MSI and Gigabyte Technology have followed suit with the MSI K9ND MS-9282 and MSI K9SD MS-9185 resp. the M57SLI-S4 models.

Some BIOSes contain a "SLIC", a digital signature placed inside the BIOS by the manufacturer, for example Dell. This SLIC is inserted in the ACPI table and contains no active code. Computer manufacturers that distribute OEM versions of Microsoft Windows and Microsoft application software can use the SLIC to authenticate licensing to the OEM Windows Installation disk and/or system recovery disc containing Windows software. Systems having a SLIC can be activated with an OEM Product Key, and they verify an XML formatted OEM certificate against the SLIC in the BIOS as a means of self-activating. If a user performs a fresh install of Windows, they will need to have possession of both the OEM key and the digital certificate for their SLIC in order to bypass activation; in practice this is extremely unlikely and hence the only real way this can be achieved is if the user performs a restore using a pre-customised image provided by the OEM.

Recent Intel processors (P6 and P7) have reprogrammable . The BIOS may contain patches to the processor code to allow errors in the initial processor code to be fixed, updating the processor microcode each time the system is powered up. Otherwise, an expensive processor swap would be required.[12] For example, the FDIV bug became an expensive fiasco for Intel that required a product recall because the original Pentium did not have patchable microcode.

BIOS Chip

The Intel motherboard uses an Intel/AMI basic input/output system (BIOS), which is stored in flash memory and may be upgraded using a disk-based program. In addition to the BIOS, the flash memory contains the following:

y BIOS Setup Utility y Power-On Self Test (POST) y Advanced Power Management (APM) software y PCI automatic configuration utility y Windows 95-ready Plug and Play

This motherboard supports computer BIOS shadowing, allowing the BIOS to execute from 64- bit onboard write-protected Dynamic Random Access Memory (DRAM).

The BIOS displays a message during power-on self-test (POST) identifying the type of BIOS and the revision code.

Use the links below to explore other BIOS features.

Fan

The Glacialtech Igloo 5610 PWM is a compact LGA775 Intel heatsink suitable for office work computers. It's 80mm fan is Pulse Width Modulation compliant, so Intel motherboards can direct it to spin only as fast as required (from a low 800RPM to moderately audible 3200RPM), thus keeping unnecessary noise down. The Igloo 5610 PWM is comprised of two heatpipes, a small section of extruded aluminum heatsink and a short array of aluminum cooling fins. A very simple CPU cooler, and one that is priced in the $10-$15 range making it cost effective for office PCs.

Glacialtech's Igloo 5610 PWM heatsink weighs just 373grams, and in Frostytech's real world tests ranges from 45.4 to 59.5 dBA in noise output. The heatsink stands 100mm tall, and ships with a pre-applied of thermal compound on its base.

The only odd thing with the Glacialtech Igloo 5610 PWM heatsink is the manufacturer's choice of using screw based clips. For a heatsink this lightweight, we would have expected the standard Intel push-to-click plastic retention mechanisms used with the reference heatsinks. Instead with the Igloo 5610 PWM we find four captive screws and a metal motherboard support bracket which necessitates removing the board from the PC chassis. For a heatsink that weighs 373grams, that comes with pre-applied thermal compound, and that is best suited towards generic office PCs, this isn't a smart choice.

For system integrators, or industrial PC applications a screw based heatsink retention mechanism fits the bill. Perhaps that is the intended application here... For the time being, all Frostytech is interested in is how the Glacialtech Igloo 5610 PWM heatsink performs thermally. Let's begin the analysis. Graphics Cards

The images you see on your monitor are made of tiny dots called pixels. At most common resolution settings, a screen displays over a million pixels, and the computer has to decide what to do with every one in order to create an image. To do this, it needs a translator -- something to take binary data from the CPU and turn it into a picture you can see. Unless a computer has graphics capability built into the motherboard, that translation takes place on the graphics card.

A graphics card's job is complex, but its principles and components are easy to understand. In this article, we will look at the basic parts of a video card and what they do. We'll also examine the factors that work together to make a fast, efficient graphics card.

Think of a computer as a company with its own art department. When people in the company want a piece of artwork, they send a request to the art department. The art department decides how to create the image and then puts it on paper. The end result is that someone's idea becomes an actual, viewable picture.

A graphics card works along the same principles. The CPU, working in conjunction with software applications, sends information about the image to the graphics card. The graphics card decides how to use the pixels on the screen to create the image. It then sends that information to the monitor through a cable. Creating an image out of binary data is a demanding process. To make a 3-D image, the graphics card first creates a wire frame out of straight lines. Then, it rasterizes the image (fills in the remaining pixels). It also adds lighting, texture and color. For fast-paced games, the computer has to go through this process about sixty times per second. Without a graphics card to perform the necessary calculations, the workload would be too much for the computer to handle.