Chapter 4: The System Unit Content

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The System Unit
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System Unit

• Basic types
• Desktop system units
• Notebook system units
• laptops
• Tablet PC system units
• Convertible tablet PC
• Slate tablet PC
• Handheld computer system units
• Palm computers, Personal digital assistants (PDA)

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The System Unit
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Competencies

• 1. Binary Codes
• 2. System Board
• 3. Microprocessor
• 4. Memory
• 5. Bus lines
• 6. Expansion Slots and Cards
• 7. Ports

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Overview

• Computing power
• Speed, capacity, and flexibility
• System unit
• Houses motherboard (processor chip memory
  chips), power supply storage devices
• Functionality of basic components of CPU
• Basic principles
• Representation of data programs

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3.1 Representation of Data and Instructions

• Cannot understand human language
• Represented electronically
• Conversion must occur
• Understand machine language, which is represented
  by a binary system

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3.1.1 Binary System

• Two-state numbering system of 0 and 1
• 0 or 1 is called a bit (short for binary digit)
• 0 can be represented by electricity being off and
  1 by electricity being on
• Bits are combined into groups of eight bits
  called bytes
• Each byte represents one character

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3.1.2 Principal Schemes

• ASCII
• EBCDIC
• Unicode

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ASCII

• American Standard Code for Information
  Interchange
• 8 bits
• 256 character combinations, conventional
  characters, math symbols Greek letters
• Widely used binary code for microcomputers

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EBCDIC

• Extended Binary Coded Decimal Interchange Code
• 8 bits
• Large computers such as mainframes
• Developed by IBM and primarily used on large
  computers

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Unicode

• Uses two bytes for each character rather than one
• 16-bit code to support international languages
  like Chinese and Japanese
• 65536 character combinations
• Complete representation of languages that have
  many characters
• Support by Apple, IBM Microsoft

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Importance of Schemes

• Providing a language for computers to understand
• Sharing using files on different computers
  application
• Conversion programs are available

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3.1.3 Parity Bit

• Dust, electrical disturbances, weather conditions
  other factors cause interference transmitting
  byte
• Use parity bit an extra bit attached
• Two parity scheme
• Even parity
• Odd parity
• Message Parity Error call technician

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3.1.3 Parity Bit (cont)
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3.2 Power Supply

• Alternating current (AC) from wall outlet
• Microcomputer runs on direct current (DC)
• Power supply converts AC to DC
• Need power protection device
• Surge protector protects against spikes (high
  voltage)
• Voltage regulator protects from insufficient
  power
• Uninterruptible power supply (UPS) provides
  electricity if power fails

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3.2 Power Supply (cont)
UPS
Surge protector
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3.3 System Board

• Large, flat circuit board located inside the
  computer
• Main board or motherboard
• Allows communication between all devices
• Connects all components thru bus lines
• Circuit board contains
• Soldered, non removable components
• sockets or slots for removable components such as
  microprocessor chip, RAM chips, various
  expansion cards
• Removable components allow to expand or upgrade
  system

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3.4 Chip or Microchip

• Fundamental part of motherboard
• Miniaturized circuitry board etched on a small
  tiny postage-stamp-sized square
• An integrated circuit embodies solid-state
  technology - electrons are traveling through
  solid material (silicon)
• Silicon found in clay and sand - abundance and is
  a semiconductor
• Called silicon chip, semiconductor, integrated
  chip
• Mounted on carrier packages, which are then
  plugged into sockets on the system board

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3.4 Chip (cont)

• Transistors current chips have 9.5-43 millions
  microminiature electronic circuit components
• Types of microchips
• Memory
• Logic
• Communications
• Graphics
• Math
• Microprocessor
• Microcontroller

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Steps in Manufacture of a Microchip

• Make large drawing. Reduce drawing hundreds of
  times to microscopic size.
• Duplicate reduced photo many times on sheet.

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Steps in Manufacture of a Microchip

• Print sheet of multiple copies on a wafer made of
  silicon, a semiconductor.
• Print layer after layer above and below original
  silicon surface.

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Steps in Manufacture of a Microchip

• Cut wafer into chips.
• Mount chip in frame with connective pins
  extruding.

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3.4.1 Microprocessor Chip

• Single chip that contains the central processing
  unit (CPU) of the computer
• CPU is the brains of the computer system
• Stores program instructions
• Two principal architectures CISC RISC
• Different processing speeds

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3.4.1 Microprocessor Chip (cont)

• Capacity is expressed in word size
• Number of bits that can be accessed at one time
  by the CPU
• Common sizes are 16 bits (2 bytes), 32 bits (4
  bytes), or 64 bits (8 bytes)
• The more bits in a word, the more powerful and
  faster
• Two kinds of microprocessors used in most
  personal computers today
• Intel-type chips made by Intel, AMD, and others
• Motorola-type chips made by Motorola for Apple
  Macintosh computers

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3.4.1 CPU

• Known also as processor
• Follows instructions of software to manipulate
  data into information
• Communicate with rest of PC through
  interconnected chips called chipset
• Contains
• Control unit
• Arithmetic/logic unit
• Registers or high-speed storage areas
• Linked by electronic roadway called bus

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Control Unit

• Deciphers each instruction stored in it carries
  out the instruction
• Direct movements electronic signals between main
  memory and arithmetic/logic unit
• Directs the control signals between the CPU and
  input-output devices
• For each instruction, control unit do 4 basic
  operations - machine cycle
• Fetches, Decodes, Executes, and Store

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Machine Cycle
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Arithmetic/Logic Unit (ALU)

• Performs arithmetic operations logical
  operations
• Controls speed of these operations
• Arithmetic operations
• Addition, subtraction, multiplication, division
• Logical operations
• Compares data whether data if equal to (), less
  than (lt), or greater than (gt) another.

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Registers

• Special high-speed storage areas that temporary
  store data during processing
• Used by control unit ALU to enhance computers
  performance
• Store
• Program instruction while being decoded
• Data while processed by ALU
• Results of calculation
• Types
• Instruction, address, storage, accumulator
  registers

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Buses

• Or bus lines where bits are transmitted
• Within CPU
• Between CPU components of motherboard
• Multilane highway
• More lanes the faster bits transferred
• 8-bit, 32-bit, 64-bit (Pentium), 128 (Macintosh
  G4 supercomputers)

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How the Processor or CPU works Control Unit,
ALU, Registers
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Specialized Processor Chips

• Coprocessors
• Parallel processor
• Smart Cards

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Smart Cards

• Use a tiny built-in microprocessor
• Two types Intelligent smart card Memory card
• Size of a credit card
• hold specialized data such as health insurance
  information, frequent flier records, drivers
  license information, etc
• American Express and Visa have recently
  introduced smart credit cards
• MyKad???

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3.4.2 Chipsets

• Chipsets determine types of
• Processors, memory, video card ports that
  work on same motherboard
• Multimedia, storage, network, other hardware
  motherboard support
• Intels chipset 850 works with Pentium 4
  processor

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3.4.3 Architecture Of Microprocessor Chip

• CISC complex instruction set computer
• RISC reduced instruction set computer
• Todays processor include
• MMX technology to enhance multimedia processing
• SSE instructions (Intel) or 3DNow! Technology
  (AMD) to facilitate web graphics 3D graphics

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CISC

• Used mostly on PCs Conventional mainframes
• Large number of instructions
• Low processing speeds
• Intel-type chips for PCs made by
• Intel Corp, Advanced Micro Devices (AMD), Cyrix,
  DEC others
• Used by manufacturers such as
• Compaq, Dell, Gateway, Hewlett-Packard, IBM
• Chips names
• Pentium, Pentium Pro, Pentium MMX, Pentium II,
  III, Celeron, and Pentium IV (P4) (42 million
  transistors)

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RISC

• Used mostly on workstation
• Seldom-used instructions eliminated
• 10 times faster than most PCs
• Made by Motorola for Apple Macintosh computers
• Motorola, IBM, Apple produce PowerPC chips
  since 1993
• PowerPC can run PC as well as Mac applications
  software

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3.4.3 Processing Speeds

• Microprocessor contains system clock
• Controls how fast all operations take place
• Uses fixed vibrations from quartz crystal that
  deliver digital pulses or ticks called cycles
• Synchronizes operations
• Expressed in megahertz
• Faster clock speed, faster computer
• Processing speeds are measured for
• Microcomputer - megahertz gigahertz
• Workstations, minicomputers, mainframe MIPS
• Supercomputers flops
• All computers fractions of a second

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Megahertz Gigahertz

• Megahertz (MHz) measure frequency equivalent to 1
  million cycles per second
• Original IBM PC had clock speed 4.77 MHz
• Pentium III processes 933 million cycles/second
• Latest generation, Intel AMD, operate in
  gigahertz (GHz), 1 billion cycle per second
• Pentium 4 operates up to 1.9 GHz
• Predicts a 50GHz to support speech interfaces
  real-time translation
• Intels mobile processors Pentium III runs 450
  MHz -1GHz, Celeron 450-850 MHz
• Recommend fret less about speed spend more on
  extra memory

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MIPS

• Stands for millions of instructions per second
• Measured according number of instructions per
  second computer can process
• High-end microcomputer or workstation perform at
  100 MIPS or more
• Mainframe at 200-1200 MIPS

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flops

• Stands for floating-point operations per second
• Special mathematical calculation
• Used mainly by supercomputers
• megaflops or mflops or millions, gigaflops or
  gflops or billions, teraflops or tflop or
  trillions of floating-point operations per
  second
• Option Red 1.34 teraflops. 1 second of Option Red
  equivalent 31,000 years of completing one
  arithmetic calculation every second
• New supercomputers measured up to petaflops or 1
  quadrillion operations per second

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Fractions Of A Second

• Another way of measuring cycle time
• Microcomputer in microseconds
• Supercomputer in nanoseconds or picoseconds
  (thousands or millions faster)
• Speed units
• Milllisecond Thousand of a second
• Microsecond Millionth of a second
• Nanosecond Billionth of a second
• Picosecond Trillionth of a second

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Processing Speeds From Megahertz to Picoseconds
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3.5 Memory

• Other silicon chips attached to motherboard
• Holds data for processing, instructions for
  processing the data, and information waiting to
  be output or sent to secondary storage
• Type of memory chips are
• RAM
• ROM
• CMOS
• Flash
• Cache
• Speeding up processing by interleaving, bursting,
  pipelining

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Memory Measure
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3.5.1 RAM Chips

• RAM - Random access memory also called memory or
  main memory.
• Primary storage that temporary holds
• Software instructions
• Data before after processed by CPU
• Volatile for now. M-RAM available in 2004/5
• Types of RAM chips DRAM, SDRAM, SRAM, RDRAM
• Get more memory by buying single or in module
• Types of memory modules are SIMMs or DIMMs

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3.5.1 RAM Chips (cont)
SIMM
DIMM
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3.5.2 Types Of RAM Chips

• DRAM (dynamic RAM)
• Constantly refreshed by CPU
• SDRAM (synchronous dynamic RAM)
• Synchronized by system clock, much faster than
  DRAM, speed expressed in MHz
• SRAM (static RAM)
• Faster than DRAM, retain contents without
  refreshed by CPU
• RDRAM (Rambus dynamic RAM)
• Faster more expensive than SDRAM, used with
  Intels P4

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3.5.3 RAM Size

• Microcomputers come with different RAM size
• 64MB SDRAM, 128 megabytes of RAM
• More RAM implies
• Faster computer operates
• Better software performs
• Check how much RAM needed before purchasing or
  installing new software
• Not enough memory, OS support program to run
  using virtual memory
• Large programs divided into parts
• Needed part are read into RAM

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3.5.4 ROM Chips

• Read-only memory - also known as firmware
• Store fixed start-up instructions
• Cannot be written on or erased without special
  equipment
• Contain special fixed start-up instructions for
  computing operations
• Loaded with special instructions for basic
  computer operations
• Start the computer
• PROM programmable read-only memory allows user
  to load read-only programs and data only once

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3.5.5 CMOS Chips

• Store flexible start-up instructions - can be
  reprogrammed
• Complementary metal-oxide semiconductor
• Powered by battery
• Dont lose contents when power off
• Contain essential information required when
  computer turned off - reflect changes
• Contain flexible start-up instructions
• Time, date, calendar
• Amount of RAM
• Type of keyboard, mouse, monitor, disk drives

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3.5.6 Flash Memory Chips

• New type of RAM that is not temporary
• Store flexible programs
• Can be erased reprogrammed more than once
• Capacity of 1-64 megabytes
• Store programs in computers, pagers, cellphones,
  MP3 players, palm organizer, printers, digital
  cameras.
• Expensive than hard disk
• Will replace disk tape storage

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3.5.7 Cache Memory

• Temporary stores instructions and data that
  processor likely to use frequently
• Acts as high-speed, temporary holding area
• CPU runs much faster than RAM, waits for
  information
• Faster processing results
• Two kinds Level 1 (L1) Level 2 (L2)
• Current OS allow use virtual memory
• Use hard disk space
• Search LI first, then L2, then RAM, then hard
  disk or CD-ROM. From fast to the slowest

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LI Cache

• Level 1 cache known as internal cache
• Built into processor chip
• 8-256 Kbytes less than L2 cache
• Operates faster than L2 cache

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L2 Cache

• Not part of microprocessor chip
• Usually in ads.
• Called external cache
• Consists of SRAM chips
• Capacities 64 kilobytes to 2 megabytes
• Intel ads called Advanced Transfer Cache
• Connected to CPU by backside bus

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3.6 Speeding Up Processing

• Memory chips on motherboard effect system
  performance
• Speed data travel between memory CPU is
  critical
• Distance between CPU RAM is another critical
  performance factor
• Methods to speed up processing are interleaving,
  bursting, pipelining

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3.5.8 Virtual Memory

• Concept of dividing a large program into parts
  and storing the parts on a secondary device, such
  as a hard disk, during processing
• Free hard-disk space used to extend the capacity
  of RAM
• Each part of the program is read into RAM only
  when needed
• Most of todays operating systems support virtual
  memory

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3.6.1 Interleaving

• Interleaving refers CPU alternates communication
  between 2 or more memory
• Large systems such as servers workstation
• SDRAM chips divided, interleaving produces
  continuous flow of data

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3.6.2 Bursting

• Bursting provides CPU additional data based on
  likelihood next data needed
• CPU grabs block of information instead of one
  piece of data
• Saves time

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3.6.3 Pipelining

• Divides task into stages that are overlapped with
  some work completed
• CPU fetch next instruction before present
  instruction complete
• Available on PCs
• Each processor can pipeline up to 4 instructions

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3.7 Expansion Slots and Cards

• Closed architecture open architecture
• Expansion slots are sockets on motherboard into
  which expansion cards can be plugged
• Expansion cards are also known as expansion
  boards, adapter cards, interface cards, plug-in
  boards, controller cards, add-ins, or add-ons
• Provide more memory or that control peripheral
  devices

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3.7 Expansion Slots and Cards (cont)

• Connect to different types of buses
• CPU memory is system bus or memory bus or
  frontside bus (FSB)
• CPU expansion slots (thus peripheral devices)
  is expansion bus
• Universal serial bus (USB) eliminate need
  expansion slots card
• Port allows cable to be connected to a device
  outside the system unit
• Plug and Play is set of hardware software that
  can configure new devices systems automatically

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3.7 Expansion Slots and Cards (cont)
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3.7 Kinds Available

• Network Interface Card
• SCSI adapter
• Television boards
• PC cards
• Graphic card
• Sound card
• Modem card
• Other cards

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3.7.1 Network Interface Card (NIC)

• Known as network adapter card
• Connect a computer to one or more computers on a
  communication network
• Allows transmission of data over cable network
• Connects various computers other devices such
  as printers
• User can share data, programs, hardware over
  the communication network.

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3.7.2 SCSI Card

• Small computer system interface card
• Limited number of expansion slots can use SCSI
  card in one slot
• Can connect up seven devices
• Devices such as printers, hard disk drives
  CD-ROM

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3.7.3 Television Boards

• TV turner cards
• Contain TV video converter that changes TV
  signal to be displayed on monitor
• Can watch TV surf Internet at same time
• Lead to specialized large screens with high
  quality audio called home PCs
• Refer to Making IT Work for You Oleary
  OLeary

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3.7.4 PC Cards

• Thin, credit card-sized expansion board for
  portable computers to expand capabilities -
  easily inserted and replaced
• Called Personal Computer Memory Card
  International Association or PCMIA cards
• Increased memory (flash RAM), sound cards, modem,
  hard disks, pagers, cellular communicators and
  connecting to other computers

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3.7.4 PC Cards (cont)

• Three types
• Type I, thin, for flash memory
• Type II, thick, for fax modems network
  interface cards
• Type III, thickest, rotating disk devices, hard
  disk drives wireless communication devices

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3.7.5 Graphic Card

• Included in all PCs
• Called video card or video adapter
• Converts computer signals into video signals as
  images on monitor
• Example is 3-D AGP (Accelerated Graphics Port)
  card
• 8, 16, 32 MB

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3.7.6 Sound Card

• For speakers audio output
• Used to record and play back digital sound
• Transmit digital sounds through speaker,
  microphones, and headsets
• Installed on new PCs
• PCI wavetable sound cards add music sound
  effect to games
• Wavetable synthesis create music from recordings
  of actual instrument

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3.7.7 Modem Cards

• For remote communication via telephone lines
• Internal external modems
• Sends receives digital data over telephone
  lines to from computers
• Can transmit voice fax signals

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3.7.8 Other Cards

• Accelerator board - speeds up processing, turbo
  board or upgrade board
• Cache card - improves disk performance
• Coprocessor board - specialized processor chips
  that increase processing speed
• Disk controller card - allow certain type of disk
  connected
• Emulator board - microprocessor as terminal for
  larger computer system
• Memory expansion board - enable additional RAM
  to be added
• CD-ROM Card - Used to connect optical disk drives

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3.7.9 Plug and Play

• A computer system needs to be reconfigured when
  an expansion board is added
• Plug and play eliminate reconfiguration tasks -
  require setting special switches on the expansion
  board and creating special configuration files
• Developed by Intel, Microsoft, and others
• With plug and play, operating systems, processing
  units, and expansion boards are able to configure
  themselves

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3.8 Bus Lines

• Known as data bus or simply a bus
• Circuitry in a computer
• Data roadway for travelling bits
• Links the CPU to various other components on the
  system board
• More lanes, faster traffic - 64 bit bus faster
  than 32 bit bus
• Change in microprocessor chips has created a
  change in bus lines
• Many devices, such as expansion boards, will work
  with only one type of bus line

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The Frontside Bus
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3.8.1 Principal Architectures

• Industry Standard Architecture (ISA)
• Peripheral Component Interconnect (PCI)
• Accelerated Graphics Port (AGP)

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ISA Bus

• Industry Standard Architecture Bus
• Developed for IBM Personal Computer
• Most widely used expansion bus
• The oldest
• The slowest - 8 or 16 bits, used for mouse, modem
  cards, low-speed network cards

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PCI Bus

• Peripheral Component Interconnect Bus
• Variety of purposes
• Meet video demands of graphical user interfaces
• High-speed 32-64 bit, 20 times faster ISA
• Most recently developed category of buses called
  local buses
• Most widely used local bus
• Connect CPU, memory, graphics cards, sound cards,
  modems, high speed network cables

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AGP Bus

• Accelerated Graphics Port bus
• Newest twice as fast PCI bus
• Dedicated to acceleration of graphics performance
• Used for graphics 3-D animination
• Replacing PCI for transfer of video data

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3.9 Ports

• Connecting socket or jack outside system unit
• Seven common ports
• Serial
• Parallel
• SCSI
• USB
• Dedicated
• Infrared
• FireWire
• AGPs

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3.9 Ports (cont)
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3.9.1 Serial Ports

• For transmitting slow data over long distances
• Send data one bit at a time
• Wide variety of purpose
• Connect mouse, keyboard, monitors, modem, many
  devices
• 9-pin, 25-pin RS-232C Connector

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3.9.2 Parallel Ports

• External devices that need to send or receive lot
  of data over short distance (15 feet)
• Used to connect printers to the system unit
• Send 8 bits of data simultaneously across 8
  parallel wires
• Mostly used to connect printers or external disk
  or magnetic tape backup storage devices to system
  unit

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3.9.3 SCSI Ports

• Small computer system interface ports
• Allow data transmitted in daisy chain up to 7
  devices
• At speeds (32 bits) higher than serial or
  parallel ports
• Connect external hard disk drives, CD-ROM drives,
  scanners, magnetic-tape backup units
• Daisy chain means devices connected in series
• Internal external daisy chain

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3.9.3 SCSI Ports (cont)
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3.9.4 USB Ports

• Universal serial bus
• One port can be used to connect several devices
  to the system unit
• Faster than serial or parallel ports
• Expected to replace serial and parallel ports
• Transmitting data up to 127 devices in daisy
  chain to one general-purpose port
• Useful for peripherals such as digital cameras,
  digital speakers, scanners, high-speed modems,
  joysticks
• Permits Plug and Play that allow peripheral
  devices expansion cards automatically
  configured while installing

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3.9.4 USB Ports
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3.9.5 Dedicated Ports

• Keyboards, mouse, phone, speaker, microphone,
  modem-to-telephone others
• Special purpose ports
• Power plug socket is not a port!!

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3.9.6 Infrared Ports

• Cableless connections over few feet with
  infrared-capable devices such as printers
• Similar concepts to remote TV controller
• Requires unobstructed line of sight
• Only a few feet apart

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3.9.7 FireWire Ports

• HPSB - High Performance Serial Bus
• Newest type
• Faster than USB ports
• Connect high speed printers, video cameras to
  system unit

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3.9.8 AGPs

• Accelerated graphics ports
• Connect monitors
• Support high-speed graphics other video input

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3.10 Cables

• Connect IO devices to system unit via ports
• Most common cables
• Mouse
• Keyboard
• Printer
• Monitor

• Newer cables
• AGP graphics monitor
• USB joy stick, scanner
• HPSB video camera

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Future Processors
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Summary
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Web Assignments

• Microprocessors - To learn more about Intel most
  recent microprocessors, visit http//www.intel.com
  /intel/product/index.htm. Once connected to the
  site, select two current microprocessors. Print
  out the pages that best describe each
  microprocessor. Write a paragraph comparing the
  two.

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Web Assignments (cont)

• Universal Serial Bus - USB is the next evolution
  of computer ports. It was developed through the
  collaboration of seven leading-edge companies. To
  learn more about this technology, visit the Yahoo
  site at http//www.yahoo.com and search using the
  keywords USB and universal serial bus.
  Follow several of the links to learn more and
  print the Web page you find the most informative.
  Write a brief summary of what you learned about
  USB.

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Web Assignments (cont)

• Desktops and Notebooks - There are several sites
  on the Web from which you can learn more about
  the newest desktops and notebooks on the market
  today. Visit http//www.pcworld.com/top400 to
  link to one of these sites. Once connected to
  that site, check out the different models and
  select the one that best meets your needs. Print
  out the specifications for your chosen computer
  and write a paragraph describing how this
  computer best suits your needs.