Computer Chapter 4

7/29/2019 Computer Chapter 4

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System Unit

Case that contains electronic components of the

computer used to process data

Made of plastic or metal and protects the internal

electronic components from damage


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Motherboard system board

Main circuit board of the system unit

Contains slots for adapter cards, processor chips andmemory

Adapter card: circuit boards that provide connections and

functions not build into the motherboard (sound card,video card)

Memory: holds data waiting to be processed andinstructions waiting to be executed

Computer chip: small piece of semiconducting material,usually silicon, on which integrated circuits are etched

Integrated circuit: contains many microscopic pathwayscapable of carrying electrical current; contains millions ofelements (resistors, capacitators, transistors)


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Processor

Central processing unit (CPU) Interprets and carries out the basic information

Impacts overall computing power

Manages most of the computers operations

On a personal computer: all functions of theprocessor are usually on a single chip

Microprocessor: personal computer processor chip

Processor core: contains the circuitry necessary toexecute instructions


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Control Unit

Directs and coordinate most of the operations in

the computer

traffic cop

Interprets each instruction issued by a program

Initiates the appropriate actions to carry the

instruction

Controls the internal components:arithmetic/logic unit and buses


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Arithmetic Logic Unit (ALU)

- performs arithmetic, comparison and otheroperations

Arithmetic Equations

- Basic calculations: addition, subtraction,multiplication, division

Comparison Equations

-Comparing one data item with another todetermine whether the first item is greaterthan, equal to, or less than the other item


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Machine Cycle

-For every instruction, a processor repeats a set offour basic operations

1. Fetching 2. Decoding

2. 3. Executing 4. Storing (if necessary) Fetching

process of obtaining a program instructionor data item from a memory

Decoding- process of translating the instruction intosignals the computer can execute


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Executing

- process of carrying out commands

Storing- writing the result to memory (not to a

storage medium)


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The System Clock

- A small quartz crystal circuit controls the timing

of all computer operations.

- Generates regular electronic pulses, or ticks that

set the pace of components of the system unit.

Clock speed - measure of the number of ticks per

second.

*current personal computers have clock speeds in the gigahertz range (one billion of

the system clock per second)


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* The faster the clock speed, the more

instructions the processor can execute per

second


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Comparison of Personal Computer

Processors

- Intel and AMD are the leading manufacturers

of personal computer processor chips.

- High-performance desktop personal

computers today use a processor in the Intel

Core family.

- Basic personal computers today use a brand of

Intel processor in the Pentium or Celeron

Family


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- Xeon and Itanium families of processors are

ideal for workstations and low-end servers.

- AMD is the leading manufacturer of Intel-

compatible processors


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Data Representation

- Only two discrete states: on and off

- Two digits, 0 and 1, easily can represent thesetwo states

- 0: off 1: on

Binary System

- a number system that has just two

unique digits, 0 and 1, called bits. Bit (binary digit)

-smallest unit of data the computer can

process


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Byte

- 8 bits grouped together

-provides enough different combinationsof 0s and 1s to represent 256 individual

characters (includes numbers, uppercase

and lowercase letters of the alphabet,

punctuation marks etc.)


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Memory

- Consists of electronic components that storeinstructions waiting to be executed by theprocessor.

- Consists of one or more chips on themotherboard or some other circuit board in thecomputer

- Stores 3 basic categories of items

1. The Operating System and other systemsoftware that control or maintain thecomputer and its devices


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2. Application programs that carry out a

specific task (such as word processing)

3. The data being processed by the

application programs and resulting

information

Stored program concept

- The role of memory to store both data

and programs


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Bytes and Addressable Memory

Byte

-basic storage unit in memory

-Each byte resides temporarily in a location

in memory that has an address Address

- is a unique number that identifies thelocation of the byte in memory

To access data or instructions in memory, thecomputer references the address that containsbytes of data.


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Memory Sizes


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TYPES OF MEMORY

2 types: (when the computers power is turnedoff)

Volatile memory

loses its contents

temporary

Nonvolatile memory does not lose its contents

Permanent


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VOLATILE MEMORY

RAM (Random Access Memory)

main memory

consists of memory chips that can be read from

and written to by the processor and other devices.

when the computers power is turned on, certain

operating system files load into the RAM from a

storage device such as the hard disk. These filesremain as long as there is continuous power in the

computer.


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3 basic types:

Dynamic RAM (DRAM; DEE-ram)- must be re-

energized constantly or they lose their contents. Static RAM (SRAM; ESS-ram)- faster and more

reliable than any variation of DRAM chips. Theydo not need to be re-energized as often asDRAM.

Magnetoresistive RAM (MRAM; EM-ram)-stores data using magnetic charges instead of

electrical charges. Manufacturers claim thatMRAM has greater storage capacity, consumesless power, and has faster access times thanelectronic RAM.


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Memory module- a small circuit board

Memory slots- hold memory modules and arefound on the motherboard.

RAM Configurations Amount of RAM necessary depends on what kind

of software you want to use

More RAM=faster computer Amount of RAM purchased today ranges from 1-

128 GB


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USER DESCRIPTION AMOUNT OF RAM

A (home) -Has latest version of

Windows-basic application

software

1GB of RAM

B (business) -work with

accounting, financial,and spreadsheet

programs

-also, programs with

multimedia

capabilities

2-8 GB of RAM

C -Creating professional

Web sites or graphic-

intensive applications 8 GB of RAM


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NONVOLATILE MEMORY

CACHE (cash)

Two Types: Disk cache

Memory cache it stores frequently used instructions two types:

L1 cache- built directly in the processor chip.

8KB-128 KB

L2 cache- slower but has a larger capacity than L1

64KB-16MB

Advanced transfer cache- 512 KB-12MB

L1 L2 RAM


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ROM (rahm) Read-only Memory

memory chips storing permanent data andinstructions

data in it cannot be modified

Firmware- ROM chips that contain permanent

written data, instructions, or information.

FLASH MEMORY can be erased electronically and rewritten

most computer use flash memory to hold their startupinstructions

on mobile computers and devices

Flash memory cardscontain flash memory on a

removable device instead of a chip


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CMOS (SEE-mos)

complimentary metal-oxide semiconductor

high speed and consumes little power

uses battery power

The flash memory chips that store a computers

startup information often use CMOS technology


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Memory Access Times

Access time- amount of time it takes a

processor to read data, instructions, and

information from memory.

accessing data on memory- 200,000 times

faster than accessing data on a hard disk

while access times of memory greatly affect

overall computer performance, manufacturers

and retailers usually list a computers memory

in terms of its size, not its access time.


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TERM ABBREVIATIO

N

SPEED

Millisecond ms One-

thousandth of

a second

Microsecond s One-millionth

of a second

Nanosecond ns One-billionth

of a second

Picosecond ps One-trillionth

of a second


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EXPANSION SLOTS AND ADAPTER

CARDSExpansion slot

a socket on the motherboard that can hold anadapter card

Adapter card

a circuit board that enhances functions of acomponent of the system unit and/or providesconnections to peripherals

Sometimes called an expansion card

Peripheral

a device that connects to the system unit and is controlledby the processor in the computer (e.g., modems, disk drives,printers, scanners, and keyboards)


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Some motherboards include all necessary capabilities and donot require adapter cards. Others may require adapter cards

to provide capabilities such as sound and video.

Sound card

enhances the sound-generating capabilities of apersonal computer by allowing sound to be inputthrough a microphone and output through externalspeakers or headphones.

Video card

also called graphics card; converts computer

output into a video signal that travels through a cableto the monitor, which displays an image on the screen


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Removable Flash Memory

Memory card

a removable flash memory device whichis inserted and removed from a slot in apersonal computer, game console, mobile

device, or card reader/writerusually no bigger than 1.5 in height orwidth

USB flash drive

a flash memory storage device that plugs ina USB port on a computer or mobile device


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Express Card slot

a special type of expansion slot that holds a PC Cardor an ExpressCard module

o PC Card

a thin, credit card-sized removable flashmemory device that primarily is used today

to enable traditional notebook computersand Tablet PCs to access the Internetwirelessly

o Express Card module

about one-half the size of a PC Card and adds

memory, communications, multimedia, andsecurity capabilities to computers


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Ports and Connectors

Port

the point at which a peripheral attachesto or communicates with a system unit so

that the peripheral can send data to orreceive information from the computer

sometimes called jack to identifyaudio and video ports

Connector

joins a cable to a port


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USB PORTSUSB portUniversal Serial Bus port

can connect up to 127 different peripheralstogether with a single connector

USB 2.0 or Hi-Speed USB

a more advanced and faster USB, with speeds 40 timeshigher than that of its predecessor

USB 3.0

even faster than USB 2.0

Both USB 2.0 and USB 3.0 are backward compatible, which means theysupport older USB devices as well as newer USB devices.

USB hub

a device that plugs in a USB port system unit and contains multipleUSB ports in which you plug cables from USB devices


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FIREWIRE PORTSFireWire port

previously called IEEE 1394 portSimilar to a USB port in that it can connect multiple

types of devices that require faster data transmission

speeds, such as digital video cameras, digital VCRs, color

printers, scanners, digital cameras, and DVD drives, to a

single connector

Allows you to connect up to 6 devices together

FireWire hub

used to attach multiple devices to a single FireWireport

A device that plugs in a FireWire port on the system

unit and contains multiple FireWire ports in which you

plug cables from FireWire devices


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OTHER PORTS

Bluetooth Port

Bluetooth technology uses radio waves to transmit databetween two devices given that they have to be within about33 feet of each other.

SCSI Port

a special high-speed parallel port which allows you to attachSCSI (/skuhzee/) peripherals such as disk drives and printers

o SAS (serial-attached SCSI) a newer type of SCSI thattransmits at much faster speeds than parallel SCSI

eSATA Port

external Serial Advanced Technology Attachment port

allows you to connect a high-speed external SATA hard disk toa computer


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IrDA Port

used by wireless devices to transmit signals to acomputer via infrared light waves

MIDI Port

Musical Instrument Digital Interface (/MID-dee/)

a special type of port that connects the system unit to amusical instrument, such as an electronic keyboard

O Synthesizer

creates sound from digital instructions;

can be a peripheral or a chip

A system unit with a MIDI port has the capability of recording

sounds that have been created by a synthesizer and then

processing the sounds (the data) to create new sounds.


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PORT APPLICATIONS AND DOCKING

STATIONS

Port replicator an external device that

provides connections to peripherals through

ports built into the device

Docking station an external device that

attaches to a mobile computer or device,

contains a power connection and providesconnections to peripheral


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Buses

Bus it allows the various devices both inside

and attached to the system unit to

communicate with each other

It consists of two parts:

data bus used to transfer actual data

address bus used to transfer information about

where the data should reside in memory


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Bus width size of a bus, it determines thenumber of bits that the computer can transmit atone time

A computer has three basic types of buses:

System bus or Front side bus (FSB) a part of themotherboard and connects the processor to mainmemory

Backside bus (BSB) it connects the processor tocache

Expansion bus it allows the processor tocommunicate with peripherals


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Bays

Bay an opening inside the system unit in

which one can install additional equipment

Drive bay a rectangular opening that typically

holds disk drives

External bay it allows a user to access openings

in the bay from outside the system unit

Internal bay concealed entirely within thesystem unit


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Power Supply

Power supply the component of the system

unit that converts the wall outlet AC power

into DC power

Wall outlets supply an alternating current (AC) of115 to 120 volts, and a computer requires a direct

current (DC) ranging from 5 to more than 15 volts

AC adapter an external power supply, it convertsthe AC power into DC power that the peripheral

requires


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K i Y C M bil


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Keeping Your Computer or Mobile

Device Clean

The system unit collects dust over time and

this can block airflow in a computer or mobile

device which can cause it to overheat, corrode

or even stop working.

So cleaning your computer or mobile device

once or twice a year will help it extend its life.


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It i t i f b i d t


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Its maintenance requires a few basic products: Can of compressed air removes dust and lint from

difficult-to-reach areas; removes sticky liquid spilled

on keyboards Lint-free antiseptic wipes and swabs

Screen cleaning solution or 50/50 mix of rubbingalcohol and water (do not use ammonia-basedsolutions)

Small computer vacuum Antistatic wristband to avoid damaging internal

components with static electricity

Small screwdriver - may be required to open the case

or remove adapter cards You can have a local professional or computer

company to clean the inside of your desktop ornotebook computer case for you.


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Documents

Computer Chapter 4