6666CH

AP

TE

R

THE SYSTEM UNIT

6-2

© 2005 The McGraw-Hill Companies, Inc. All Rights Reserved.

Competencies

Describe the four basic types of system units

Discuss how a computer uses binary codes

Describe the major system unit components

Describe system boards, microprocessors, and memory

Describe the function of the system clock, expansion slots, boards, and bus lines

Discuss ports, cables, and power supply

6-3

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System UnitsMicrocomputers

Desktop

Notebook

Tablet PC

Handheld

6-4

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Electronic Data and Instructions

Data and instructions are represented electronically

Computers recognize digital signals

Binary systemBit

Byte

6-5

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Binary Coding Scheme

Two state systemOff/on electrical states

Characters represented by 0s and 1s

Three types of schemesASCII - American Standard Code for Information Exchange

EBCDIC - Extended Binary Coded Decimal Interchange Code

Unicode

6-6

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Binary Code

Code Uses

ASCII Microcomputers

EBCDIC Large Computers

Unicode International Languages

6-7

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System Board

Connects all components

Allows communication between devices

Main board or motherboard

Circuit board electronic components

Sockets

Slots

Bus lines

6-8

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Microprocessor

Central Processing Unit (CPU )

Two basic components Control unit

Arithmetic and logic unit

6-9

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Microprocessor Chips

Chip capacities are expressed in word sizes

Types of microprocessor chipsCISC chips: Complex instruction chips

Most widely used design

Used by Intel

RISC chips: Reduced instruction set computer chipsUses fewer instructions

Design is simpler and less costly

Used by the PowerPC

6-10

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Specialty Processors

Graphics coprocessors

Parallel processors

Smart cards

6-11

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Memory

Holding area for data, instructions, and information

Types of memory chipsRAM – holds programs and data

ROM – fixed start-up instructions

CMOS – flexible start-up instructions

6-12

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Memory Capacity

UnitUnit CapacityCapacity

Megabyte (MB) 1 billion bytes

Gigabyte (GB) 1 million bytes

Terabyte (TB) 1 trillion bytes

6-13

© 2005 The McGraw-Hill Companies, Inc. All Rights Reserved.

System Clock

Important measurement indicating speed Located on a small chip

Produces electrical beats

Synchronizes operations

Expressed in gigahertz

Faster clock speed, faster computer

What is a gigahertz?

6-14

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Expansion Slots and Cards

Allow for new devices to be addedOpen architecture

Slots provide for expansion

Expansion cards are also called …Plug-in boards

Controller cards

Adapter cards

Interface cards

6-15

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Commonly Used Expansion Cards

Video cards

Modem cards

Network interface cards (NIC)

TV tuner cards

PC cards

6-16

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Bus Lines

Connect parts of the CPU to each other

Data roadway for traveling bitsMeasured as bus width

More lanes, faster traffic

Two basic categoriesSystem buses

Expansion buses

6-17

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Types of Expansion Buses

Industry Standard Architecture (ISA)

Peripheral Component Interconnect (PCI)

Advanced Graphic Port (AGP)

Universal serial bus (USB)

FireWire buses HPSB – high performance serial bus

Used with digital camcorders & video editing software

6-18

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Ports

Socket for connecting external devices

Four common portsSerial

Parallel

USB

FireWire

6-19

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Power Supply

Computers require direct current (DC)

DC power provided by converting alternating current (AC) from wall outlets or batteries

Desktop computers use power supply units

Notebooks and handhelds use AC adapters

AC adapter

Power Supply Unit

6-20

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A Look to the FutureXybernaut Corporation

Wearable computersCalled POMA Includes…

Windows CEWireless pointing deviceHead-mounted displayMP3 playerAbridged Windows Office programs

6-21

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Key Terms

AC adapter (164)accelerated graphics port (AGP) (163) adapter card (159)alternating current (AC) (164)analog (151)arithmetic operation (155)Arithmetic logic unit (AL

ASII (152)

binary coding scheme (152)

binary system (151)

bit (151)

bus (162)

bus line (154)

bus width (162)

byte (151)

6-22

© 2005 The McGraw-Hill Companies, Inc. All Rights Reserved.

Key Terms

video card (159)

video capture card (159)

video recorder card (159)

volatile storage (157)

virtual memory (157)

word (155)

workstation (155)

6-23

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FAQs

What are the four basic types of system units?

What is analog? What is digital?

What is a microprocessor and what does it do?

What is RAM? What is ROM?

I hear a lot about flash memory. What is it?

I need a USB port to install a wireless mouse. What are ports?

What is a network card?

6-24

© 2005 The McGraw-Hill Companies, Inc. All Rights Reserved.

Discussion Questions

Explain how a computer understands instructions.

Define memory and describe three types of memory chips.

Explain the purpose of expansion cards and slots. Give examples of some commonly used expansion cards.

Describe how bus lines work.