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)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 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.