Chap5 System Unit Primary Storage

8/3/2019 Chap5 System Unit Primary Storage

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` What is the system

unit? Case that contains

electronic

components of the

computer used to

process data

x Sometimes called

the chassis

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Memory Adapter cards

Sound card Modem card

Video card

Network

card Ports Power supply

power supply

ports

drive bays

processor

memory

sound card

video cardmodem card

network card

Processor


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` What is the

motherboard? Main circuit board

of the system unit. Contains

expansion slots,

processor chips,

and memory slots.

Also called systemboard.

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CPU/ProcessorCPU/Processor

ControlControl

UnitUnit

ArithmeticArithmetic

Logic Unit (ALU)Logic Unit (ALU)

ArithmeticArithmetic

Logic Unit (ALU)Logic Unit (ALU)

InputInput

DevicesDevices

StorageStorage

DevicesDevices

OutputOutput

DevicesDevices

Interprets and

carries out basic

instructions thatoperate a

computer

MemoryMemoryDataData InformationInformation

InstructionsInstructions

DataData

InformationInformation

InstructionsInstructionsDataData

InformationInformation

ControlControl

UnitUnit


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2.1 CPU or microprocessorsConsists of two major parts which are:

Control units

Tells the rest of thecomputer systems howto carry out a program'sinstruction.For each instruction, the

control unit repeats a set

of 4 basic operations knowas machine cycle (Fetch,

Decode, Execute, Store).

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Control ALU 1

2 3

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ALUPerforms arithmetic operation and logical operationsand controls the speed of the operation.

Arithmetic operation - performs four kinds ofarithmetic operations or mathematical calculations:+, -, X and /.Logical operation - comparisons such as ==, >=,


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3.0 System Unit3.1 MotherboardMotherboardThe main circuit board in the system unit which holds:

The CPU or microprocessor .

Electronic memory that assists the CPU, known as RAM.

And some expansion slots where additional circuit boards,

called expansion boards may be plugged in.

processor chipadapter cards

memory chips

memory slots

motherboard

Expansion

slots for

adapter cards


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EXPANSION SLOT


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Memory Devices

(RAM,ROM,PROM,EPROM) Storage Devices

(Auxiliary Storage Devices-Magnetic Tape,

Hard Disk, Floppy Disk)

(Optical Disks: CD-RDrive, CD-RW

disks,DVD, Blu ray Discs)

3.3Memory


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1111

3.3.13.3.1 Types of System UnitTypes of System UnitMemoryMemory

volatile memoryLoses its contents when

computer's power

is turned off

nonvolatile

memoryDoes NOT lose its

contents when

computers power is

turned off


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3.3.23.3.2 Main MemoryMain Memory (RAM)(RAM)Also known as primary storage, internal memory, random

access memory (RAM) or memory .

Is a working storage with following tasks :

It holds data for processingHolds instructions to process data

Holds data after it is processed, waiting to be sent to an

output or secondary storage device

Its content are temporary / volatile .

Size determines total size of programs and data files thatthe computer can work at any time.

More memory more data faster.


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` What are two basic types of RAM chips?

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Must beMust be

refreshedrefreshed

constantlyconstantly

Do not have toDo not have tobe refreshedbe refreshed

as often asas often as

DRAMDRAM

MostMostcommoncommon

typetype

Faster andFaster and

more reliablemore reliable

than DRAMthan DRAM

chipschips

DynamicDynamicRAMRAM

(DRAM)(DRAM)

StaticStaticRAMRAM

(SRAM)(SRAM)


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` Summary:1. SRAM is static (Dont refreshed periodically) while DRAM is

Dynamic (refreshed periodically

2. SRAM consists of Transistor while DRAM made up of

Transistors & Capacitor3. SRAM consumes less power than DRAM

4. SRAM is more expensive than DRAM

5. SRAM is faster compared to DRAM

6. Cheaper DRAM is used in main memory whileSRAM is

commonly used in cache memory

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3.3.2 Read-only memory (ROM) Contains programs and data that are permanently

recorded at the factory.

Can be read and used, but cannot be changed bythe user.

ROM is nonvolatile.


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3.3.3 CMOS

To store information about the computer such as:

The type of disk drives, keyboard and

monitor.

The current date and time, and other startup

information. Use battery power to retain information even

when the power to the computer is turned off.


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` Types of ROMs

Programmable ROM (PROM)

Erasable programmable ROM (EPROM)

Electrically erasable PROM (EEPROM)

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Helps speed computer processes by storing

frequently used instructions and data.

Also called memory cache.

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It has hot swapfeatures you dont

have to reboot the

system

USB is plug and play

USB (universal serial bus) port can connectup to 127 different peripherals together

with a single connector type (USB hub)


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What are Ethernet ports?Also known as RJ-45 jack.

To connect computer to a LAN.

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Chap5 System Unit Primary Storage