chap4-5 system board

8/2/2019 Chap4-5 System Board

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System board is complex printed circuitboard (PCB), which is the central partof many electronic systems, particularlythe computer.

The basic purpose of the system boardlike a backplane which is to provide the

electrical and logical connections bywhich the other components of thesystem communicate.

Definition of system board


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Types of System Boards

Primary purpose of system board To house the CPU and allow all devices to

communicate with it

Two popular types AT (older)

ATX (newer)

AT and ATX differ not in overall performance,but in size, convenience features, type ofcase into which they fit, and type of powerconnection they have


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Summary of AT and ATX

Boards


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AT and ATX Boards


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System Board Components

A CPU and itsaccompanying chipset

A system clock

ROM BIOS

A CMOS

configuration chipand its battery

RAM

RAM cache

A system bus with

expansion slots Jumpers

Ports that come

directly off the board Power supply

connections


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System Board


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System Board


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Selecting a System Board(cont)

CPU types and speeds

Chip set on the board

Memory cache type and size Types and number of expansion slots

Type of memory

Maximum amount of memory you canput on the board; incremental amountsby which memory can be upgraded

continued


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Selecting a System Board

Type of case

ROM BIOS

Type of keyboard connector Presence/absence of proprietary video &/or

proprietary local bus slots

Presence/absence of IDE adapters and SCSI

controller Presence/absence of COM ports, LPT ports,

and mouse port


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Major Manufacturers of System

Boards


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The CPU and the Chip Set

Microprocessor chips are made by Intelor one of its competitors

Common model numbers 8088, 8086, 80286 (historical interest)

386 (occasional)

486 and Pentium (most familiar)


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Attributes for Rating CPUs

CPU speed measured in megahertz

Efficiency of programming code

Word size (internal data path size) Data path

Maximum number of memory addresses

Amount of memory included with the CPU Multiprocessing ability

Special functionality


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Relating CPU Attributes to Bus

Architecture

Number of memory addresses

Determined by the number of traces, or

wires, on the bus that are used for memoryaddresses

Data path size

Determined by the width of the bus datapath, or the number of parallel wires in thebus data path


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The Earlier Intel CPUs


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The Earlier Intel CPUs

Voltages used by CPUs

Early CPUs: 5 volts

Later versions of 80486Sx and 80486DX4: 3.3volts

First Pentium: 5 volts

All other Pentiums: 3.3 and 2.8 volts

Coprocessor used with older CPUs Performs calculations for the CPU at a faster

speed that the CPU


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The Pentium and Its

Competitors

True 64-bit chip

Both the data path and word size are 64

bits

Two arithmetic logic units

Can perform two calculations at the same

time


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Comparing Chips

Bus speed

Speed or frequency at which the data on

the system board is moving

Processor speed

Speed or frequency at which the CPU

operates Usually expressed in megahertz

continued


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Comparing Chips

Multiplier Factor by which the bus speed or

frequency is multiplied to get the CPUclock speed

Memory cache A small amount of faster RAM that stores

recently retrieved data, in anticipation ofwhat the CPU will request next, thusspeeding up access


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Location of L1 and L2 Caches


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Types of Pentium CPUs


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Classic Pentium

The first Pentium (introduced in 1993)

No longer manufactured


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Pentium MMX (Multimedia

Extension)

Targets the homemarket

Speeds up graphicalapplications

Performs well withgames and

multimedia software


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Pentium Pro

Recommended for 32-bit applications thatrely heavily on fast access to large amountsof cache memory

First Pentium to offer Level 2 cache insideCPU housing

Popular for computing-intensive workstations

and servers Does not perform well with older 16-bit

applications software written for DOS orWindows 3.x


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Pentium II

Popular choice for a powerful businesscomputer using graphics applications, such

as 3-D graphic manipulation, CAD, andmultimedia presentations with graphics,motion video, and sound

Designed for graphics-intensive workstations

and servers First Pentium to use a slot instead of a socket

to connect to the system board

continued


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Pentium II

Celeron processor Low-end Pentium II processor that targets the low-

end multimedia PC market segment

Uses Level 2 cache within processor housing

Works well with Windows 9x

Xeon processor Fast, high-end Pentium II processor designed

exclusively for powerful servers and workstations

Supports up to eight processors in one computer

Recommended for use with Windows NT andUNIX operating systems


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Pentium III

Uses Slot 1 and runs with the 100-MHzmemory bus with a processor speed of

500 MHz Introduced Intels new performance

enhancement called SSE, a new

instruction set designed to improvemultimedia processing even further


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The Pentium Competitors


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Competitors of the Advanced

Pentiums


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Pentiums


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Pentiums


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CPUs That Use RISC

Technology

CPU is limited to a very few instructionsthat can execute in a single clock cycle

Can process much faster when fewcomplex calculations are required

Ideal for video or telecommunications

applications Easier and cheaper to manufacture


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CPU Cooling Fans

Maintaintemperature at 90 to

110 degrees F Used to prevent

system errors and toprolong the life of

the CPU


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CPU Slots and Sockets

The physical connection used to connect theCPU to the system board

Four most common types Socket 7

Used on 66MHz boards

Super Socket 7

Used on 100MHz boards Socket 8

Slot 1


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Types of Sockets Used by CPUs


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Socket Comparisons


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The ZIF (Zero Insertion Force)

Socket

Uses a small lever to apply even forcewhen installing the microchip into socket


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Pentium II and Pentium III

Chips

CPU is completely enclosed within ablack housing


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CPU Voltage Regulator

Controls the amount of voltage on the systemboard

Dual voltage CPU Requires two different voltages, one for internal

processing and the other for I/O processing

Single voltage CPUs

Requires one voltage for both internal and I/Ooperations


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CPU Voltage Regulator


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The Chip Set

Set of chips on the system board thatcollectively controls the memory cache,

external buses, and some peripherals


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Chip Set Manufacturers

Intel Corporation

AMD, Inc.

Cyrix Corporation Silicon Integrated

Systems Corp.(known as SiS)

StandardMicrosystems Corp.

UnitedMicroelectronicsCorp.

VIA Technology, Inc.

VLSI Technology


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The Intel Chip Set Family


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Chip Sets that Compete with

Intel

VIA and AMD

VIA Apollo VP2/97

AMD-640 () SiS

Genesis

Trinity

5591/92 AGP

ALi

Aladdin Pro II

Aladdin V VIA

Apollo MVP3


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Intel Dominates the Chip Set

Market

Chip sets are more compatible withPentium family of CPUs

Huge investment in research anddevelopment

PCI bus

Universal serial bus Advanced graphics port (AGP)


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ROM BIOS

There is one ROM chip on the systemboard that contains BIOS, which

manages the startup process (startupBIOS) and many basic functions of thesystem (system BIOS)

Identifying name of BIOS manufacturer

Appears at beginning of boot process

On top of the chip (larger than most chips)


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ROM BIOS

Does the BIOS support Plug and Play?

Does the BIOS support large hard

drives? Is the BIOS chip a Flash ROM chip?


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The Total BIOS in your System


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Plug and Play BIOS

Plug and Play A technology in which the operating

system and BIOS are designed toautomatically configure new hardwaredevices to eliminate system resourceconflicts (such as IRQ and port conflicts)

Common in ROM BIOS made after 1994 ESCD (extended system configuration

data)


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When BIOS Is Incompatible

with Hardware or Software


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Most new devices are supported bydevice drivers

Upgrade BIOS with Flash ROM


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Flash ROM

EEPROM (electronically erasableprogrammable read-only memory)

Allows you to upgrade system BIOSwithout having to replace the ROM chip

S Si f


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Sample Web Site for Flash

ROM BIOS Upgrades

continued

S l W b Si f Fl h


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Sample Web Site for Flash

ROM BIOS Upgrades

RAM (R d A


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RAM (Random Access

Memory)

In older machines

Existed as individual chips socketed to the

system board in banks of nine chips each Each blank held one byte by storing one bit

in each chip; ninth chip held a parity bit


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Current Types of RAM

Dynamic RAM (DRAM) Most commonly used type of system memory

Access speeds range from 70 to 50 nanoseconds

Hold data for a very short time

Requires refreshing every few milliseconds

Static RAM (SRAM) Contains information without the need for

refreshing, as long as the computers power is on

Hold data until power is turned off

More expensive than traditional DRAM


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Dynamic Memory

Types

Parity

Error-checking scheme in which a ninth, orparity, bit is added

Value of parity bit is et to either 0 or 1

Non parity

ECC (error checking and correction)

Detects and corrects errors

M t P l T f RAM


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Most Popular Types of RAM

Modules

P ili M


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Prevailing Memory

Technologies


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Static Cache Memory

Two kinds

L1

Contained on the CPU microchip L2

External to the chip

Housed either on the system board or inside the

CPU case


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Wait States

A clock tick in which nothing happens,used to slow down the CPU so the rest

of system-board activity can keep up


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Buses and Expansion Slots

Earliest PC

Had only a single and simple bus (8-bit ISA

bus) Todays PCs

Have four or five buses, each with different

speeds, access methods, and protocols


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Bus Evolution

Data path and speed

Local buses (system buses)

Work in sync with the CPU and the system clock Example: memory bus

Expansion buses

Work asynchronously with the CPU at a much

slower rate Example: ISA bus


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Why So Many Buses?

Speeds of different hardwarecomponents evolve at different rates

Single speed for all components is nolonger practical

S t b d B i


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System-board Buses in

Common Use


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What a Bus Does

Draws electrical power

Carries control signals that coordinate

all activity Passes memory addresses from one

component to another

Passes data

Se en B s Connections on


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Seven Bus Connections on

Expansion Cards


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Buses

ISA bus 8-bit industry standard architecture bus used on

the original 8088 PC

Micro channel architecture (MCA) bus A proprietary IBM PS/2 bus, seldom seen today,

with a width of 13 or 32 bits and multiple mastercontrol, which allowed for multitaskiing

EISA (extended ISA) bus 32-bit bus that can transfer 4 bytes a a time at a

speed of about 20 MHz

continued


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Buses

Universal serial bus (USB) Designed to make installation and

configuration of I/O devices easy, providingroom for as many as 127 devices daisy-chained together

Uses only a single set of resources for alldevices on the bus

Expected to eventually replace serial andparallel ports


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USB Ports


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FireWire

An expansion bus that can also beconfigured to work as a local bus

Expected to replace the SCSI bus,providing an easy method to install andconfigure fast I/O devices

Also called IEEE 1394


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Local I/O Buses

A local bus that provides I/O deviceswith fast access to the CPU

Must connect to the CPU by way of thememory bus

Example of a Proprietary Local


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Example of a Proprietary Local

Bus


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Local I/O Buses

VESA (Video Electronics StandardsAssociation) VL bus Used on 80486 computers for connecting 32-bit

adapters directly the the local processor bus Has been replaced with the PCI bus

PCI (peripheral component interconnect) bus Common on Pentium computers

Runs at speeds of up to 33 MHz, with a 32-bit-wide data path

Serves as the middle layer between the memorybus and expansion buses


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VESA Local Bus


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PCI Bus


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PCI Bus


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Accelerated Graphics Port

A slot on a system board for a videocard that provides transfer of video data

from the CPU that is synchronized withthe memory bus


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Accelerated Graphics Port

Bus Comparisons and Bus


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Bus Comparisons and Bus

Speeds


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On-Board Ports

Ports that are directly on the systemboard, such as a built-in keyboard port

or on-board serial port


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Hardware Configuration

Communicates to the CPU what hardwarecomponents are present in the system andhow they are set up to interface with the CPU

Provided on system board in three ways

DIP switches

Jumpers

CMOS (retains data even when computer isturned off)


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Chapter Summary

System board

Central site of computer logic circuitry

Location of the most important microchip inthe computer, the CPU

chap4-5 system board

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