The Components of the System Unit
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The Components of the System Unit The System Unit What is the system unit? system unit ¾ Case that contains electronic components of the computer used to process data Sometimes called the chassis system unit system unit system unit p. 4.04 Fig. 4-1 Next 1 The System Unit What are common components inside the system unit? ¾ Processor power supply drive bays ¾ Memory ¾ Adapter cards processor Sound card Modem card memory ports Video card Network card ¾ Ports sound card ¾ Drive bays ¾ Power supply video card network card modem card p. 4.03 Fig. 4-2 Next The System Unit adapter cards What is the motherboard? processor chip ¾ Main circuit board in system unit ¾ Contains adapter memory chips cards, processor chips, and memory chips ¾ Also called memory slots system board or Expansion slots for main board adapter cards motherboard http://computer.howstuffworks.com/motherboard.htm/printable p. 4.04 Fig. 4-3 Next 2 Background The original IBM PC contained the original PC motherboard. In this design, which premiered in 1982, the motherboard itself was a large printed circuit card that contained the 8088 microprocessor, the BIOS, sockets for the CPU's RAM and a collection of slots that auxiliary cards could plug into. If you wanted to add a floppy disk drive or a parallel port or a joystick, you bought a separate card and plugged it into one of the slots. This approach was pioneered in the mass market by the Apple II machine. By making it easy to add cards, Apple and IBM accomplished two huge things: 1. They made it easy to add new features to the machine over time. 2. They opened the computer to creative opportunities for third-party vendors. Motherboards 3 Data Bus Width Modern Pentium class motherboards have a data bus with 64 bits. That is the width of the data highway that goes in and out of the processor. The Pentium processors, however, do use 32-bit registers to handle 32-bit instructions. Bus speeds and widths have increased due to faster processors and the needs of multimedia applications. Typical bus names and widths are: 1. Industry Standard Architecture (ISA) - 8 or 16 bits 2. Peripheral Component Interconnect (PCI) - 32 or 64 bits 3. Accelerated Graphics Port (AGP ) - 32 bits The System Unit dual inline packages (DIP) What is a chip? holds memory chips ¾ Small piece of semi-conducting material on which integrated circuits are etched Integrated circuits contain many microscopic pathways capable of carrying electrical current pin grid ¾ Chips are packaged so they can array (PGA) package be attached to a circuit board holds processor chips p. 4.04 Fig. 4-4 Next 4 Central Processing Unit What is the central processing unit (CPU)? ¾ Interprets and carries Processor out basic instructions Control Arithmetic that operate a computer Unit Logic Unit (ALU) Control unit directs and Information coordinates operations in Data computer Information Arithmetic logic unit Input Output (ALU) performs Data Information Devices Data Memory Information Devices arithmetic, comparison, Devices Devices and logical operations Information ¾ Also called the processor Data Information Storage Devices Next http://computer.howstuffworks.com/microprocessor.htm/printable Central Processing Unit What is a machine cycle? ¾ Four operations of the CPU comprise a machine cycle Step 1. Fetch Obtain program instruction or data item from memory Memory Step 2. Step 4. Store Decode Write result to memory Translate instruction into Processor commands ALU Control Unit Step 3. Execute Carry out command p. 4.06 Fig. 4-6 Next 5 Central Processing Unit What is pipelining? ¾ CPU begins fetching second instruction before completing machine cycle for first instruction ¾ Results in faster processing p. 4.07 Fig. 4-7 Next Central Processing Unit What is a register? (***) ¾ Temporary high-speed storage area that holds data and instructions Stores location from where instruction was fetched Stores Stores data instruction while it is while ALU being decoded computes it Stores results of calculation p. 4.07 Next 6 Chipsets Chipsets provide the support for the processor chip on the motherboard. The chipset is the heart of the computer since it controls and determines how fast and which type of processor, memory, and slots are used. Another chip on the motherboard is called the Super I/O controller. Its main function is to control the floppy disk drive, keyboard, mouse, serial and printer ports. Check out PCGuide's Super I/O Controller Functions to learn more. Recent motherboard designs include additional chips to support USB, sound card, video adapter, computer host and network adapter. These chips save the cost of an adapter slot. Central Processing Unit What is the system clock? ¾ Controls timing of all computer operations ¾ Generates regular electronic pulses, or ticks, that set operating pace of components of system unit Pace of system clock is clock speed Processor speed can Each tick Most clock speeds are also be measured in is a in the gigahertz (GHz) millions of instructions clock cycle range (1 GHz = one per second (MIPS) billion ticks of system clock per second) p. 4.07 Next 7 Central Processing Unit How do personal computer processors compare? Comparison of Widely Used Personal Computer Processors Name Date Clock Introduced Speed ® Itanium 2 2002 1 GHZ and up Xeon™ 2001 1.4–2.4 GHZ Itanium® 2001 733–800 MHZ ® Pentium 4 2000 1.4–2.53 GHZ Pentium ® III Xeon™ 1999 500–900 MHZ Pentium ® III 1999 400 MHZ–1.2 GHZ Celeron® 1998 266 MHZ–1.8 GHZ Operon™ 2003 To come Athlon™ MP 2002 1.53–1.6 GHZ Athlon™ XP 2001 1.33–1.73 GHZ Athlon™ 1999 500 MHZ–1.4 GHZ p. 4.08 Next Central Processing Unit What is a zero-insertion force (ZIF) socket? ¾ Allows you to install and remove chips with no force lever lever Step 1. Step 2. Step 3. Lift the lever on the socket. Insert the chip. Push the lever down. p. 4.11 Fig. 4-10 Next 8 Central Processing Unit What are heat sinks and heat pipes? ¾ Heat sink—component with fins that cools heat sink fan processor ¾ Heat pipee—smaller device for notebook computers heat sink p. 4.12 Fig. 4-11 Next Central Processing Unit What is a coprocessor? ChipChip thatthat assistsassists processorprocessor inin performingperforming specificspecific taskstasks OneOne typetype isis aafloating floating-point-point coprocessorcoprocessor,, alsoalso knownknown asas aa mathmath oror numericnumeric coprocessorcoprocessor p. 4.12 Next 9 Central Processing Unit What is parallel processing? ¾ Using multiple Control Processor processors simultaneously to execute a program faster Processor 1 Processor 2 Processor 3 Processor 4 ¾ Requires special Memory Memory Memory Memory software to divide problem and bring results together Results combined p. 4.12 Fig. 4-12 Next Data Representation How do computers represent data? ¾ Most computers are digital Recognize only two discrete states: on or off Use a binary system to recognize two states Use Number system with two unique digits: 0 and 1, called bits (short for binary digits) http://computer.howstuffworks.com/bytes.htm/printable p. 4.13 Fig. 4-13 Next 10 Data Representation What is a byte? ¾ Eight bits grouped together as a unit ¾ Provides enough different combinations of 0s and 1s to represent 256 individual characters Numbers Uppercase and lowercase letters Punctuation marks p. 4.13 Fig. 4-14 Next Data Representation What are three popular coding systems to represent data? ¾ ASCII—American Standard Code for Information Interchange ¾ EBCDIC—Extended Binary Coded Decimal Interchange Code ¾ Unicode—coding scheme capable of representing all world’s languages ASCII Symbol EBCDIC 00110000 0 11110000 00110001 1 11110001 00110010 2 11110010 00110011 3 11110011 p. 4.14 Next 11 Data Representation How is a letter converted to binary form and back? Step 1. The user presses Step 2. the capital letter D An electronic signal for the (shift+D key) on capital letter D is sent to the the keyboard. system unit. Step 4. Step 3. After processing, the binary The signal for the capital letter D code for the capital letter D is is converted to its ASCII binary converted to an image, and code (01000100) and is stored in displayed on the output device. memory for processing. p. 4.15 Fig. 4-16 Next Memory Seat #2B4 Seat #2B3 What is memory? ¾ Electronic components that store instructions, data, and results ¾ Consists of one or more chips on motherboard or other circuit board ¾ Each byte stored in unique location called an address, similar to addresses on a passenger train http://computer.howstuffworks.com/computer-memory.htm/printable p. 4.15 Fig. 4-17 Next 12 adapter cards processor chip memory chips memory slots Expansion slots for adapter cards motherboard Memory How is memory measured? ¾ By number of bytes available for storage Term Abbreviation Approximate Size Kilobyte KB or K 1 thousand bytes Megabyte MB 1 million bytes Gigabyte GB 1 billion bytes Terabyte TB 1 trillion bytes p. 4.16 Fig. 4-18 Next 13 Memory What is random access memory (RAM)? Memory chips that can be read from and written to by processor Most RAM is Also called volatile, it is lost main memory when computer’s or primary power is storage turned off The more RAM a computer has, the faster it responds p. 4.17 Next Memory How do program instructions transfer in and out of RAM? RAM Step 1. When you start the computer, certain operating system files load into RAM from the Operating system Operating system hard disk. The operating system displays the user instructions interface interface on the screen. Step 2. When you start a Web browser, the program’s instructions load into RAM from the Web browser Web browser hard disk.