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Chapter 06The System Unit

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Competencies

After you have read this chapter must be able

to:

1. Describe five principal types of expansion

buses.2. Compare standard, specialized, and legacy

ports.

3. Discusspower supply for desktop and

notebook computers.

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Bus Lines

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Bus Lines

A bus line is also called a bus Connect parts of the CPU to each other

Data roadway for traveling bits.

Measured as bus width

More lanes, faster traffic

Every computer has two basic

categories of buses:

Two basic categories:

1.System buses:connects the CPU to

memory on the system board

2.Expansion buses :connects the CPU

to slots on the system board

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Expansion Buses

Connects the CPU to other components on the

system board, including expansion slots

Principal types:

1) Peripheral Component Interconnect (PCI) . 2) Universal serial bus (USB) 3) FireWire buses

4) Serial Advanced Technology Attachment (SATA)

5) PCI Express (PCIe)

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1) Peripheral Component Interconnect :

originally for video demands of GUI (graphical

user interfaces); widely used to connect CPU,

memory, and expansion boards; either 32 or 64bit, more than twenty times faster than an ISA

2) Universal serial bus :

gradually replacing serial and parallel portsFaster than AGP bus.

New version is USB 2.0

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Expansion Buses

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3) FireWire buses :

High-performance serial bus (HPSB)operate much like

the USB buses and perform at speeds comparable to USB

2.0

Used with digital camcorders Used with video editing software

4) SATA :

newest bus; It is much faster than USB 2.0 and FireWire

buses and is now widely used to connect high-speed

storage devices to the system board.

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1. PCI Express :

widely used I many of todays most powerful

computers; provides a single dedicated path foreach connected device; now replacing the PCI

bus.

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Expansion Buses

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Ports

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Ports

Socket for connecting external devices Portscan connect directly to the system board or

they can connect to cards that are inserted into

slots on the system board.

Portsare connecting sockets on the outside of asystem unit.

Ports are often standard features of computer

systems and others are more specialized

Three Types:

Standard Ports

Legacy Ports

Specialized Ports

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Standard Ports

Four common ports:

1. VGA

2. USB ports

3. FireWire ports4. Ethernet ports

Return

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Standard Ports

Four common ports

USB ports (universal serial bus)gradually replacing serial andparallel ports; can connect multipledevices; faster than parallel

FireWire ports also known as high

performance serial bus (HPSB) portsfor high-speed printers and videocameras; as fast as USB 2.0

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Legacy Ports

Serial portsdata transported one bit at a time;

mouse, keyboard, modem, etc.

Parallel ports for external devices needing lots

of data over short distances, like printers,scanners, external Zip drives

Keyboard and mouse ports :

Infrared data association (IrDA):

were used to provide wireless mechanisms for

transferring data between devices; for example,

transferring data from a handheld to a desktop

Game ports

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Specialized Ports

Three specialized ports

1) Musical Instrument digital interface (MIDI)

2) Sony/Philips Digital Interconnect Format (S/PDIF)

3) High Definition Multimedia Interface (HDMI)1. MIDIspecial type of serial port for connecting musical

instruments.

2. S/PDIFalso known as optical audio connections; these

ports are used to integrate computers into high-end audio

and home theatre systems .

3. HDIMprovide high definition video and audio

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Cables

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Cables

Used to connect external devices to the system

unit via the ports

One end of the cable is attached to the device

and the other end has a connector that isattached to a matching connector on the port

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Power Supply

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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 unitslocated within the system unit.

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Notebooks and handhelds use AC adapters

Notebook computers use AC adapters that are

located outside the system unit

Power Supply