Chapter 4 The Components of the System Unit Jeremy Lukianovich
The system unit The system unit is the case that contains the electronic components that make up a computer. The mother board is the main circuit board that all of the electronic components are in some way connected to.
Computer Chip The computer chip is a small piece of etched semi-conducting materiel, such as silicone. There are two types of attachments 1) DIP-dual inline package (two rows of metal feet) 2) PGA-Pin grid array (large number of pins covering the surface of the chip)
Processor-(CPU) • The Control unit- directs and coordinates activities in the computer • The arithmetic logic unit- performs comparisons, arithmetic, and logic operations • Machine cycle- the repeated 4 steps to all computer actions (1-fetching, 2-decoding, 3-executing, 4-storing) • Registers-Small storage locations in the processor. This is a high speed temporary storage area. • The system clock- controls timing of all computer operations
Processor installation and upgrades • Three types • Chip for Chip-Replace existing chip • Piggy back-stack new one on top of old chip • Daughterboard upgrade-new chip on adapter card that plugs into motherboard • Heat sinks and heat pipes • ceramic or metal finned components that help dissipate heat • Coprocessors • a secondary chip that aids the main processor, thereby increasing the performance of the computer • Parallel processing • Using multiple computer processors to increase the speed of the processor.
Data Representation • Computers use digital representation • Binary code • 1=on • 0=off • A single digit is a bit • 8 bits equal a byte • Two coding systems • ASCII • EBCDIC
Memory • RAM (Random access memory) • Primary memory type • Read from and written by programs • If power loss RAM is lost, unless stored • DRAM (Dynamic RAM) • Must be reenergized or will lose memory • Several types • SRAM (Static RAM) • Most stable but expensive • More RAM the faster the computer will be
Cache • Memory Cache • Stores frequently used data - speeds up computer • 3 types • L1-built into processor • L2-advanced transfer cache • L3-separate cache, must have L2 to work • Disk Cache (see chapter 7) • ROM (Read only memory) • Stores permanent data and instructions • Flash memory • Nonvolatile memory that can be erased electronically • Often contains startup instructions due to its adaptability • CMOS (Complimentary metal-oxide semiconductor) • Technologically advanced materiel that produces high speeds with low power draws. • Memory access times • The time it takes a computer to do an operation, this can be as little as 10 nano-seconds
Expansion Slots and Adapter cards • Expansion slots • Slot on computer that can hold a circuit board that in some way increases the performance of the computer. • Sound cards • Video cards • Modem cards • Network cards • PC cards and Flash memory cards • PC cards-a thin device that plugs into a computer and adds memory, storage, sounds, modem, communications, fax, or other abilities to the computer. • Flash memory cards-a card that allows a user to add data from a mobile device (such as a PDA) to a laptop.
Ports and connectors • Serial ports-a port that connects two devices and transmits 1 bite at a time, good for devices that do no require high transfer rates. • Mouse • Keyboard • Modem • Parallel ports-a port connects devices but transmits data at a higher rate than a serial port • Printers • USB ports-universal serial bus port • Can connect up to 127 peripherals together on one port. • Daisy chain them • USB hub • Hot plugging (plugging in a device without first shutting the computer down.
Special purpose ports • Firewire port • Similar to USB • Faster than USB • MIDI port (musical instrument digital interface) • Used to connect a instrument to a computer • SCSI (small computer system interface • Attach such devices as disk drives and printers • Daisy chain up to 7 to 15 devices • IrDA (infrared data ssociation) • Transfer data via infrared light waves, completely wireless • Bluetooth • Radio waves to transmit information • Similar to IrDA but you don’t need to line up the devies
Buses • Buses • The channels within a computer chip which the bits take to travel from one point to another. • Bus width dictates how many bits a computer may transmit and one time • Faster the bus speed the faster the programs will run. • System Buses • Part of the mother board • Connects processor to main memory • Expansion buses • Channels outside the main processor that transmit data into and out of the processor • ISA (industry standard bus)-slowest • Local- high speed bus that connects things such as disk drives • Accelerated Graphics port-improves speed which 3D graphics move • USB and Firewire • PC Card bus
Bays • Opening in system where you can insert additional equipment • Drive bays- rectangular openings which usually house disk or CD drives.
Power Supplies • Battery powered-primarily laptops • AC adaptor-allows the DC powered computer to be plugged into a AC power supply (wall socket) • A cooling fan is generally mounted near the power input
Mobile Computers and Devices • Laptops-small computers that have folding screens, very portable • Contain many miniaturized components which generally raises the price • Tablet PC-entire computer in the shape of a tablet. • PDA-handheld computing device, generally contain a phone book, basic word processing, and little else.