copyright 2003 the mcgraw-hill companies, inc. 1 44 chapter the system unit computing essentials

Copyright 2003 The McGraw-Hill Companies, Inc.

1

4444CH

AP

TE

R

The System Unit

computing ESSENTIALS


2

Competencies

System unit types

Coding

Memory and chips

Cards and buses

Ports and cables



3

System Unit Types

System Unit Houses electronic

components Basic components

System boardMicroprocessorMemory

Types of System

Units

Desktop

Notebook

Personal Digital

Assistant



4

Desktop Units

Non-portable

Input/Output devices

located outside the

system cabinet



5

Notebook Unit Portable

Monitor attached by

hinges

Keyboard and pointing

devices integral to the

system unit



6

PDA Units

Smallest system unit

All input/output and

secondary storage devices

integral to the system unit



7

Electronic Data & Code

Binary System

0s and 1s

Each 0 or 1 is a bit

8 bits = 1 byte



8

Binary Coding Scheme

American Standard Code for Information

Interchange (ASCII)

Extended Binary Coded Decimal Interchange

Code (EBCDIC)

Unicode



9

ASCII Widely used in

microcomputers 1 byte = 1 character Examples

Letter R is represented by 0101 0010

Number 3 is represented by 0011 0011

Character % is represented by 0010 0101



10

EBCDIC

Developed by IBM Used in mainframe computers 1 byte = 1 character Examples

Letter R is represented by 1101 1001 Number 3 is represented by 1111 0011 Character % is represented by 0110 1100



11

Unicode

Developed by Unicode, Inc. with support from

Apple, IBM, and Microsoft

Used to support international languages such as

Japanese and Chinese

2 bytes = 1 character



12

System Board

Connects all

components

Data path between

devices

Also called the main

board or motherboard



13

System Board Components

Sockets Connection points on the system board

Chips Tiny circuit boards etched into silicon wafers

Carrier Package Connects mounted chips into sockets



14

Microprocessor

The “brains” of the computer system Location of the Central Processing Unit

(CPU) Chip capacity expressed in word size

16 bit, 32 bit, 64 bit Larger the word size

faster the computer



15

CPU

Control unit Directs the movement of electronic signals

between memory and the ALU Arithmetic-logic unit (ALU)

Arithmetic operationsFundamental math operations

Logical operationsCompares data



16

Common Microprocessors CISC chip

Complex Instruction Set Computer Intel’s Pentium, Itanium chips, AMD

Athlon, Hammer chips RISC chip

Reduced Instruction Set Computer Simpler, cheaper then RISC chips Motorola PowerPC chip, DEC Alpha

chip



17

Other Microprocessors

Smart Cards

Plastic card that contains a specialized

processor chip

Stores more than 80 times data of

conventional magnetic strip

Used in credit cards, identification cards,

phone cards



18

Memory Holding area for data and

instructions Three types

Random-access memory (RAM)

Read-only memory (ROM) Complementary metal-

oxide semiconductor (CMOS)



19

Random-access Memory

Holds currently running programs and data being processed by the CPU

Volatile storage Contained data is lost when computer is

turned off Virtual memory

RAM pages saved to secondary storage until needed by CPU



20

Special RAM Types RAM cache

Frequently accessed data Acts as high-speed, temporary holding area

between CPU and RAM Faster processing results

Flash RAM Data is retained even if power disrupted Commonly used in cell phone, digital cameras



21

Read-Only Memory

Programs and data are permanently encoded

CPU can only retrieve data

Nonvolatile, cannot be changed by the user

Used for storing special instructions, such as

computer startup



22

Complementary Metal-Oxide Semiconductor Provides the flexibility and expandability for a

computer system Saves data even when computer power is shut

off Contents can be changed by the user Stores information such as amount of memory,

type of keyboard, mouse



23

Memory Measure

UnitUnit CapacityCapacity

Kilobyte (KB) 1,000 bytes

Megabyte (MB) one million bytes

Gigabyte (GB) one billion bytes

Terabyte (TB) one trillion bytes



24

System Clock

Special chip that produces precise

electrical impulses

Used to coordinate and synchronize

computer operations

Expressed in megahertz or gigahertz

Faster clock speed, faster computer



25

Expansion Slots

Slots provided to add expansion cards to the

system unit

Used on open architecture system boards



26

Expansion Cards

Expansion cards used to connect to devices

outside the system unit

Controller cards, Adapter cards, Interface

cards, plug-in boards

Usually have ports to connect the card to a

device outside the system unit



27

Types of Expansion Cards

Network interface cards (NIC)

Modem cards Sound cards Video cards SCSI adapter TV tuner cards PCMCIA cards



28

“Plug and Play”

Hardware and software standards

Makes system expansion easy for the user

Automatically installs drivers and system

configuration

System unit recognizes the new device



29

Bus Lines

More lines, the faster data can travel 64 bit data bus is

faster than a 32 bit Data pathways that

link parts of the CPU together and components to the CPU



30

Principal Bus Architectures

Industry Standard Architecture (ISA)

Peripheral Component Interconnect (PCI)

Advanced Graphic Port (AGP)

Universal Serial Bus (USB)

High performance Serial Bus (HPSB)



31

ISA Bus

Developed by IBM for personal computers

Slow

Originally 8 bit, later expanded to 16 bit

Still used by some expansion cards

Replaced by PCI bus in the near future



32

PCI Bus

Originally developed to meet demands of

graphical user interfaces

High speed

32 bit or 64 bit

Widely used to connect CPU, memory, and

expansion cards



33

AGP Bus

Dedicated bus for acceleration of graphics

performance

Replacing the PCI bus for transfer of video data



34

Other Bus Types

USB Connects directly to the PCI bus on the

motherboard Supports external devices without inserting

expansion cards for each device HPSB

FireWire Similar to USB but faster



35

Ports

Four common port types Serial Parallel USB FireWire


Sockets that connect external devices to the system unit


36

Serial & Parallel Ports

Serial Port

Data sent one bit at a time

Good long distance transmission of data

Parallel Port

Data sent 8 bits simultaneously

Used for short distances



37

USB and HPSB Ports

USB Port Replacing serial and parallel ports Faster Each port can support

more than one device HPSB Port

FireWire ports Faster then USB ports



38

Cables

Connect Input/Output devices Mouse Keyboard Printer Monitor

Newer cables AGP

graphics monitor USB

joy stick; scanner HPSB

video camera



39

Look to the Future

Wireless Technology and PDAs Personal wearable computer

POMA®

Wireless pointing device, head mounted display

Developed by Xybernaut Corporation

Currently being evaluated for use in airport security


copyright 2003 the mcgraw-hill companies, inc. 1 44 chapter the system unit computing essentials

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