6666CH

AP

TE

R

THE SYSTEM UNIT

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6-2

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

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6-3

System UnitsMicrocomputers

Desktop

Notebook

Tablet PC

Handheld

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Electronic Data and Instructions

Data and instructions are represented electronically

Computers recognize digital signals

Binary systemBit

Byte

What is the difference between digital and analog

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6-5

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( used for large computers)

Unicode ( for international languages like Chinese and Japanese.

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Binary Code

Code Uses

ASCII Microcomputers

EBCDIC Large Computers

Unicode International Languages

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System Board Main board or motherboard

Connects all components

Allows communication between devices

Circuit board electronic components

Sockets

Slots

Bus lines

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6-8

Microprocessor

Central Processing Unit (CPU )- Two basic components

Control unit Tell the rest of the computer how to carry out a program’s instructions It directs the movement of electronic signals between memory,

instructions and arithmetic logic unit. Direct control signals between the CPU and I/O devices.

Arithmetic and logic unit (ALU)Perform two types of operations

Arithmetic and logic

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6-9

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Quiz 3

Special Quiz

6-10

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6-11

Microprocessor Chips

Chip capacities are expressed in word sizes A word is the number of bits that can be accessed at one time by the CPU.

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 ( is a RISC chip produced by Motorola)

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6-12

Power PC

CISC CPU

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6-13

Specialty Processors

Graphics coprocessors(for displaying and manipulating 2-D and 3-D graphics)

Parallel processors - To run or process large programs

- Break the program into parts and assign the parts to separate processor

Smart cards (master card)

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6-14

Memory

Holding area for data, instructions, and information

Types of memory chipsRAM – holds programs and data- Virtual Memory

ROM – fixed start-up instructions

CMOS – flexible start-up instructions

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6-15

Memory Capacity

UnitUnit CapacityCapacity

Megabyte (MB) 1 million bytes

Gigabyte (GB) 1 billion bytes

Terabyte (TB) 1 trillion bytes

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6-16

System Clock

Important measurement indicating speed Located on a small chipProduces electrical beats(impulse)

Synchronizes operationsExpressed in gigahertzFaster clock speed, faster computerthe clock speed determines how many instructions per second the processor can execute

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6-17

Expansion Slots and Cards

Allow for new devices to be addedOpen architecture( allow user to expand their systems by providing slots on the system board)

Slots provide for expansion

Expansion cards are also called …Plug-in boards

Controller cards

Adapter cards

Interface cards

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6-18

Commonly Used Expansion Cards

Video cardsModem cards (internal modem)Network interface cards (NIC)TV tuner cards PC cards (PCMCIA)

Users are able to add memory, wired and wireless communications, multimedia and security

features by inserting ExpressCard modules into compliant systems Plug and play

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6-19

Bus Lines

Connect parts of the CPU to each other

Connect the CPU to other devices on the system board.

Data roadway for traveling bitsMeasured as bus width

More lanes, faster traffic

Two basic categories of Expansion BUSESSystem buses ( connect CPU to Memory)

Expansion buses ( connect CPU to slots on the system board)

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6-20

Types of Expansion Buses

Industry Standard Architecture (ISA) ( 8 or 16 bus width )

Peripheral Component Interconnect (PCI)(32 or 64 bus width)

Advanced Graphic Port (AGP)(transferring video data)

Universal serial bus (USB)To support several external devices without using expansion cards

or slotFireWire buses

HPSB – high performance serial busUsed with digital camcorders & video editing software

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6-21

PCI

ISA

AGP

USB

FireWire

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6-22

Ports

Socket for connecting external devices

Four common portsSerial

Parallel

USB

FireWire

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6-23

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

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6-24

A Look to the FutureXybernaut Corporation

Wearable computersCalled POMA Includes…

Windows CEWireless pointing deviceHead-mounted displayMP3 playerAbridged Windows Office programs

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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)

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6-26

Key Terms

video card (159)

video capture card (159)

video recorder card (159)

volatile storage (157)

virtual memory (157)

word (155)

workstation (155)

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6-27

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?

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6-28

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.