66CH

APT

ER

THE SYSTEM UNIT

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Competencies

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

Discuss ports, cables, and power supply

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System Clock

Important measurement indicating speed Located on a small chipProduces electrical beats

Synchronizes operationsExpressed in gigahertzFaster clock speed, faster computer

What is a gigahertz?

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System Clock

Controls speed and synchronizes operationsExpressed in megahertzFaster the clock speed, the faster the computer

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Expansion Slots and Cards

Allow for new devices to be addedOpen architectureSlots provide for expansion

Expansion cards are also called …Plug-in boardsController cardsAdapter cardsInterface cards

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Page 88-89

Section D

.. Expansion Slots and Cards

Expansion slot - long, narrow socket on the motherboard into which you can plug an expansion card

Graphics card (for connecting monitor)Modem (for transmitting data over phone or cable lines)Sound card (for connecting speakers)

Expansion card - small circuit board that provides computer with ability to control storage, input or output deviceMost computers have 4 - 8 expansion slots

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Do notebook computers also contain expansion slots?Most notebook computers are equipped with a special type of external slot called a PCMCIA slot (personal computer memory card international association)Typically a notebook only has one slot, but the slot can hold more than one PC card (PCMCIA expansion cards)

PC Cards

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PC card

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Commonly Used Expansion Cards

Video cardsModem cardsNetwork interface cards (NIC)TV tuner cards PC cards

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Page 92

Internal devicesTools required

ScrewdriverDirections

Before installingUnplug the computerGround yourself

InstallingFollow the directions

Installing a New Expansion Card

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Some devices require software, called a device driverThe device driver sets up communication between your computer and the deviceNormally, disk or CD used only onceToday’s PCs include Plug and Play (PnP) that automatically takes care of these technical details

.. Installing a New Expansion Card

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Installing a New Expansion Card

For installing a new device, following setup is needed:

Inserting the device card into the matching slotInstalling the device driver program for the deviceConfigure the system (tedious step, requires sufficient technical background)

“Plug and Play” is a new technology for making the device installation procedure much faster and easier.

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“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

A plug-n-play card requires the user to:

•Switch off the system

•Insert the card

•Open the system again.

•System automatically configure itself for the newly installed device

-User is asked for the latest device driver.

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Bus Lines

Connect parts of the CPU to each other Data roadway for traveling bits

Measured as bus widthMore lanes, faster traffic

Two basic categoriesSystem busesExpansion buses

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Page 88

Section DChapter

2Input and Output Devices

Expansion slots, cards and ports: How does a computer get data from RAM to a peripheral device?

Data Bus carries data from one component to anotherI/O (computer jargon for input/output) refers to collecting data and transporting results.Expansion bus - the segment of the data bus that transports data between RAM and peripheral devices

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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 busUsed with digital camcorders & video editing software

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Page 89

The microcomputer motherboard typically has up to three types of expansion slots:

ISA - older technology, modems and slow devicesPCI - for graphics, sound, video, modem or network cardsAGP - for graphics cards

Expansion cards are built for only one type of slot

… Types of Expansion Buses

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Page 89

AGP slot

PCI slot

ISA slot

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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

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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

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AGP Bus

Dedicated bus for acceleration of graphics

performance

Replacing the PCI bus for transfer of video data

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Other Bus Types

USBConnects directly to the PCI bus on the motherboardSupports external devices without inserting expansion cards for each device

HPSBFireWireSimilar to USB but faster

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Page 90

To connect a peripheral device to an expansion card, you plug a cable from the device into the expansion portExpansion port - any connector that passes data in and out of a computer or peripheral device

Expansion Ports

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Page 90

Network port

Modem port

Monitor port

Speaker and microphone jacks

Power plug socket

Parallel port (printer)

DB-9 serial port

USB ports

Mouse port

Keyboard port

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Ports

Socket for connecting external devices Four common ports

Serial ParallelUSB FireWire

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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

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USB and HPSB Ports

USB PortReplacing serial and parallel ports FasterEach port can support more than one device

HPSB PortFireWire portsFaster then USB ports

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Page 91

USB portMost popular portMost computers feature at least 2 USB portsUSB devices

MouseScannerPrinterJoystick

Windows automatically recognizes USB devices

What’s the best port to use for connectingperipheral devices?

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Cables

Connect Input/Output devices

Mouse

Keyboard

Printer

Monitor

Newer cablesAGP

graphics monitorUSB

joy stick; scannerHPSB

video camera

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Page 90-91

Major types of expansion cables

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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 unitsNotebooks and handhelds use AC adapters

AC adapter

Power Supply Unit

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Look to the Future

Wireless Technology and PDAsPersonal wearable computer

POMA®

Wireless pointing device, head mounted displayDeveloped by Xybernaut CorporationCurrently being evaluated for use in airport security