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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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Expansion Buses
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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