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It can be quite helpful to learn something about the parts that make up the

computer. This knowledge can be used for purchasing, expanding, upgrading andtroubleshooting your computer. A part merely refers to a complete stand-alone unit of

the computer such as a keyboard, monitor, or expansion card. These parts all fittogether with cables screws or edge connectors. There are only eight basic parts

(subassemblies) required to make up a functioning computers. They consist of thefollowing:

Chassis Floppy controller or multi I/OPower supply Display cardMotherboard MonitorFloppy drive (s) Keyboard

All other parts are optional and are used to enhance the capabilities of thecomputer. The more popular add-on accessories are the following.

Hard drives Memory expansion cardHard disk controllers Modems

1. Power Supply Unit - The PSU (Power Supply Unit) is an internal hardwarecomponent used to supply the components within the computer with power. Besides

properly supplying power to the computer and all its internal components, the powersupply also converts the AC electrical current found in most standard wall socketsinto a lower DC voltage that the computer components use.

ATX (Advanced Technology Extended) Switching Power Supply

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Pin Name Color Description

1 3.3V Orange +3.3 VDC


3 COM Black Ground

4 5V Red +5 VDC

5 COM Black Ground

6 5V Red +5 VDC

7 COM Black Ground

8 PWR_OK Gray Power Ok (+5V & +3.3V is ok)

9 5VSB Purple +5 VDC Standby Voltage (max 10mA) 10 12V Yellow +12 VDC


12 -12V Blue -12 VDC

13 COM Black Ground

14 /PS_ON Green Power Supply On (active low) 15 COM Black Ground

16 COM Black Ground

17 COM Black Ground

18 -5V White -5 VDC

19 5V Red +5 VDC

20 5V Red +5 VDC


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AT (Advanced Technology) Switching Power Supply

A.1 AVR (Automatic Voltage Regulator)

AVR is a device or equipment which generates, monitors, and analyzes power for a moresuitable and reliable power for computer/equipments.

Capable of:

sense over voltage and under voltage of the input line

sense over current in the load

sense aberrations in the power lines such as:- intolerable spikes transients- surges and sags- slow average fluctuations

maintains the output voltage within its tolerance ( + 1%) of the nominal voltage

responds/recover to input variations within one (1) cycle or 0.16 seconds,

usually termed as the response time.Optional:

audio/visual monitors or warnings

cut off power when such aberrations occur protecting the circuit itself andthe computer or equipment.

delay time

Types of AVR

Mechanical AVR incorporates electro-mechanical parts such as relaysand motors slow response time in terms of seconds requires maintenance heavy

Electronic AVR uses semiconductor parts in regulating voltages

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AT power connector


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quick response time in terms of milliseconds no maintenance require light in weight

A.2 U.P.S. (Uninterruptible Power Supply)

Functions of UPS

Provides continuos power to critical line

Improves/regulates quality fluctuations to sensitive loads

Protects load from voltage fluctuations

Noise and spikes caused by lightning

Electrical machines, appliances and motors

Equipments that needs

Computer mainframe and on load in the event of power line failureterminals

Telephone systems

Communication systems

Process control equipments Instrumentation equipments

Security systems

Life support systems

Nuclear power parts

Other sensitive electronics equipment

Micro-computers

UPS Parts:

1. Rectifier Charger- converts AC to regulated DC- charges the battery- input power to the inverter

2. Storage Battery- DC input to the inverter during voltage drops or upon failure ofthe normal AC line

3. Types of Battery- Lead Acid Battery

- Antimony (car battery) - Life is 3 years- Calcium - Life is 20 years

- Cost is 2 to 3 times the antimony- Nickel Cadmium - 500W or Low

- memory problem

4. Static Inverter- converts DC to AC- without moving parts

5. Static Switch- Normally use to automatically transfer load from the preferredsources to the alternate source when the preferred source is lost- Without moving parts

2. Buswire - In a computer, a bus is the data path on the computer's motherboardthat interconnects the microprocessor with attachments to the motherboard in

expansion slots (such as hard disk drives, CD-ROM drives, Floppy disk drives).

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IDE/HDD Buswire FDD Buswire3. Ports - These are connectors found at the back of the computer which send and

received data to and from the peripherals such as modems, monitors, printers,

plotters and keyboards. Ports can be found directly on the motherboard but most areadded with the use of separate expansion cards.

Serial Ports (COM Ports)These are 25-pin male connectors which are used to connect the computer to a

mouse, external modem, serial printer, plotter, graphic tablet or even anothercomputer. There are two types, 9-pin and 25-pin. The 9-pin is more frequently usedon 286 and 386 computers. The serial port itself is also referred to as an RS232 is astandard for serial communications, used in virtually all microcomputers.

Serial ports are called serial because they send and receive information seriallyor in other words, one bit at a time. These ports are also referred to as COM ports.Most computers typically have two COM ports. Each COM port is defined as eitherCOM 1 or COM 2. COM 3 and COM 4 are also available.

Parallel Port (Printer Port)Parallel ports are 25-pin female connectors. They send data in parallel that is 8

bits at a time. These ports are designated as LPT ports. LPT is an abbreviation forline printer a device commonly used with this port. Just as COM ports have a numberso do parallel ports.

Game PortThis 15-pin female connector is used for joysticks and paddles. These are

usually used to interface with game software.

PS/2 Keyboard PortThis 5-pin female connector connects the keyboard or a bar code reader to the

computer.

PS/2 Mouse PortThis 5-pin female connector connects the keyboard or a bar code reader to the

computer.

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USB Ports

USB (Universal Serial Bus) is a serial bus standard to interface

devices. It is popular with the highest speed, and security. USB supportsPlug & Play system that allows easy installation; there are many devices,

used with USB Port such as Mouse, Keyboard, Printer, Scanner, Modem,Camera Digital, etc. Mostly, the devices that interface with computer willbe USB.

4. Hard Disk Drive (HDD) It is used to store large amount of data and informationwhich can be accessed easily. The hard drive is where your programs are installedand where you save information on your computer. Lots of storage space means that

you can have a wide variety of different software.

5. Floppy Disk Drive (FDD) FDD saves information in a magnetic medium. Theinformation is stored on a removable and easily transportable floppy disk. Floppydrives come in a variety of shapes, sizes and capacities.

6. CD ROM Drive - Allows you to read data or information from compact discs (CD)

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When installing two hard drives, it is necessary tocheck the jumper setting for the Master/Slave

configuration. The jumper pins for Master/Slave can befound between the power connector and IDE ribbon

cable connector. Every hard drive manufacturer hasdifferent pin configurations which is found on theinformation pasted in the hard drive itself

Master is used for the first hard drive

Slave is for the second hard drive.

ZIP Drive100-250 MB

Super Disk120 MB

1.44 MB FloppyDisk

Floppy Disk Drive(FDD)

HDD


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7. Chassis a plastic or metal frame that holds and protects your computer parts.

There are two basic types for chassis:

Tower Case it is designed to stand

vertically that will lessen the space beingoccupied. It comes in three basic sizes: full, midi

and mini.

Desktop Case it is designed

horizontally which are usually used for office orhome PCs. It comes in two basic sizes: standard

and slimline.

8. Monitor an output device used for visual display of information.

If you are looking at your computers monitor forextended periods of time it is important to find one whichoffers the maximum comfort for your eyes. The trend with

monitors is toward ever higher resolution with increasednumber of colors.

The table shows the types of monitor and their comparative features in terms ofresolution, scanning rate and number of colors.

TYPE OFMONITOR

Resolution Color PaletteScanningRate (KHz)

MonochromeComposite

640 x 350 1 1 15.75

Color Composite 640 x 200 4 4 15.75

Monochrome(TTL)

720 x 350 1 1 18.40

RGA (CGA) 640 x 200 4 16 15.75

EGA 640 x 350 16 64 21.80

Multiscan 800 x 600 Unlimited Unlimited 15.5 to 35.0

PGA 640 x 480 Unlimited Unlimited 30

VGA 640 x 480 256 262.000 31.49

Super High 1200 x 800 + Varies Varies 30 to 75

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CD R/RW (Read/Write)

- a drive and/or media that is capable of being

written to or read from, as well as being written to or

read from many times. This term is commonly used

and found on CD-RW drives, drives capable of

recording and reading CD-RW discs.

DVD R/RW (Read/Write)

Digital Versatile Disc or Digital Video Disc, DVD

or DVD-ROM is a type ofdisc drive that allows for

large amounts of data on one disc the size of a

standard Compact Disc. DVD drives were first sold in

1997 and today are widely used for storing and

viewing movies and other data.
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Resolution - refers to the quality of the image displayed on the monitor screen and depends onthe number of dots that are present; these dots are called pixels. There are rows of pixelsgoing across as well as down the screen. The more pixels means the clearer and sharperthe image and higher the resolution. A resolution of 640 x 350 means that there are 640pixels displayed horizontal and 350 displayed vertically on the screen.

Scanning rate is the amount of time it takes for an electron gun side the monitor to draw abeam from one side of the screen to the other. The time is measured in kilohertz (KHz) orthousands of cycles per second. The faster the scanning rate the more pixels that can bedisplayed on the screen which results in a higher resolution.

Color Paletteis the full number of colors available. It should be mentioned however that all thecolors couldnt be displayed simultaneously. To display many colors with high resolutiontakes lots of memory. Since memory is still in short supply there is a choice to madeeither: you have large number of colors with limited resolution or a few colors with higher

resolution.

9. Keyboard Personal taste plays a large part in choosing a keyboard. Some peoplelike keys with a firm feel. Some prefer mushy keys. There are essentially two stylesof keyboards for the XT. First is the AT layout. Second is the IBM enhanced layout.IBM received a great deal of criticism for the keyboards it used on the PC Jr PC and

XT. When the AT was released they used a new layout; function keys on the left thestandard keyboard layout number keys on the right. This layout still had a problem

especially those working with numbers because it is necessary to toggle between thecursor pad and number pad.

A new layout with 101 keys, which it now uses on all of its computers its referred toas the Microsoft Natural layout. This layout has 12 function keys across the top and aseparate cursor and number pad. This design is rapidly becoming the industrystandard.

TYPES OF KEYBOARD

83 key PC and XT keyboard

84 key AT keyboard

101 key enhanced keyboard

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10.Mouse An input device that allows an individual to control a mouse pointer ina graphical user interface (GUI). Utilizing a mouse a user has the ability toperform various functions such as opening a program or file and does not

require the user to memorize commands

11.Motherboard The motherboard is the central subassembly in the computer. It

consist of a flat printed-circuit board on which is mounted a variety of chips and afew other components. The motherboard contains the CPU, the support circuitry ofthe socket for the CPU, the coprocessor, the BIOS chip, several rows of memory

chips and expansion slots (AGP, PCI)

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ChipsetChipset Heatsink

Socket 370 Socket A Socket 478LGA 775

Important sections of motherboard:

1) Processor socket - This is the socket on the motherboard where processor

is mounted. There are basically 3 types of slots. Socket 370 (for Via), Socket A andSocket 478 (For Pentium4 processor).

2) Chipset - Chipset is commonly used to refer to the core logic of motherboard.

Motherboard is built around a chipset that supports a specific class of processors andtype of memory. Main system chipset is responsible for the communication betweenthe processor, memory and other integrated components. Chipset acts a hubcontrolling the transfer of data between processor, its cache, system buses andperipherals. The timely transfer of data without errors is the most important functionof the chipset. This function of the chipset decides overall performance of thesystem. That is why the maximum speed of a processor that the chipset supports isvery important. For your future upgrades you will need to change only the processor.

For example, if chipset supports up to 2.8GHz CPU's and you decide to buy 2 GHz,you could upgrade to a 2.8 GHz CPU with out having to invest in new motherboard.

Different chipsets are used to support functions that are offered by the board - theRAM and the Processor. For example, the Intel 845 chipset supports Pentium 4 andDDR SDRAM. AMD processors (Duron and Athlon) require VIA KT 333 or 400 chipsetbased motherboards.

3) Interface slots - Now a days, there are basically 2 types of slots are available forADD on cards on the motherboard - PCI and AGP. PCI slots are used for adding

Ethernet card, Sound card, Modem card etc. AGP slot is used to add graphic card.

PCI Bus (Peripheral Component

Interconnect) It is 32-bit bus width,33.33 MHz clock with synchronous

transfers. The standard speed of PCIBus is half of External Bus of CPU, for

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example, bus for CPU 66 MHz PCI Bus is66/2 = 33 MHz and bus of CPU is 100and 133 MHz, PCI speed is 100/3 and

133/4.

AGP (Accelerated Graphic Port) as

well. It is the slot designed for attaching

a graphics card with maximum datarate. In a mainboard, there will be oneslot. AGP is 32-bit channel operating at

66 MHz resulting in a maximum datarate of 133 and 266 MHz.

ISA - Industry Standard

Architecture. Used when the original

8088 8bit microprocessor basedpersonal computers were produced.

4) RAM slots- DDR RAM is the most popular option today. Most motherboards have atleast two slots. But expensive motherboards have 4 slots. The total amount RAM you

can install is also dependent on the motherboard chipset.

5) BIOS - Every motherboard has special software in ROM (Read only Memory) known

as BIOS (Basic Input Output System). The jumperless motherboards that are normtoday, allow for automatic parameter detection and configuration. For example -

Processor core voltage and clock multiplier. Also the configuration and control ofintegrated peripherals are all autodetected. The BIOS is the critical part which

determines software compatibility. The BIOS is contained in one chip. The BIOS isactually the program within a chip called an EPROM (Erasable Programmable ReadOnly Memory). The EPROM contents can be erased using violet light and it is possibleto recopy a new program onto it. The program in the BIOS controls the operation ofthe computer and peripherals.

12.Video Graphics Card The graphics card plays an essential role in the PC. It takes

the digital information that the computer produces and turns it into somethinghuman beings can see. On most computers, the graphics card converts digital

information to analog information for display on the monitor; on laptops, the dataremains digital because laptop displays are digital.

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BIOS chip CMOS battery

DDRAM slot

SDRAM slot


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Here are the three basic components of agraphics card and what they do:

Memory: The first thing that a graphics

card needs is memory. The memory holds thecolor of each pixel. In the simplest case, sinceeach pixel is only black or white, you need just 1bit to store each pixel's color. Since a byte holds8 bits, you need (640/8) 80 bytes to store thepixel colors for one line of pixels on the display.You need (480 X 80) 34,800 bytes of memory tohold all of the pixels visible on the display.

Computer Interface: The second thing a

graphics card needs is a way for the computer tochange the graphics card's memory. This is

normally done by connecting the graphics card tothe card bus on the motherboard. The computercan send signals through the bus to alter thememory.

Video Interface: The next thing that thegraphics card needs is a way to generate thesignals for the monitor. The card must generate

color signals that drive the cathode ray tube(CRT) electron beam, as well as synchronization

signals for horizontal and vertical sync. Let'ssay that the screen is refreshing at 60 frames per

second. This means that the graphics card scansthe entire memory array 1 bit at a time and doesthis 60 times per second. It sends signals to themonitor for each pixel on each line, and thensends a horizontal sync pulse; it does thisrepeatedly for all 480 lines, and then sends avertical sync pulse.

13.Power Cord - Also known as a power cable, mains cable or flex a power cord is

the primary cable that provides power to the computer, printer, monitor, andcomponents within a computer. The image below is an example of the power cord

that is commonly used with computers, monitors, printers, and many otherperipherals.

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PCI Video Card

AGP Video Card

ISA Video Card

The basic parts of a graphics card are computer interface,

memory and video interface.
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14. Heatsink - With the increase of performance, heat hasbecome a big issue with computer processors and otheradvanced peripherals. If your computer processor is a Pentium

66MHz or faster processor, it is highly recommended that youensure it has a heatsink for the CPU. This part of your computer

is usually on the processor and is absolutely necessary toreduce the temperature of the processor. Since all the

information going through your computer travels through theprocessor in the form of electricity at one time or another, thisgenerates a lot of heat. A heatsink is usually made of some sortof metal and has a series of spikes and valleys. The heat fromthe processor travels to these spikes, which are then cooleddown by a fan.

15. Headset - Device connected to telephones or

computers that allow a user to talk and listen while keeping

their hands free. For example, headsets are commonly used intechnical support and customer service centers and allow theemployee to talk to a customer while typing information intothe computer.

16.Central Processing Unit (CPU) or Microprocessor - The CPU is the first thingthat comes to mind when many people think about a computer's speed and

performance. It is the heart and brain of the computer. The faster theprocessor, the faster the computer can think. In the early days of PC computers, all

processors had the same set of pins that would connect the CPU to the motherboard,called the Pin Grid Array (PGA). These pins fit into a socket layout called Socket 7.

This meant that any processor would fit into any motherboard.

Today, however, CPU manufacturers Intel and AMD use a variety of PGAs, none of

which fit into Socket 7. As microprocessors advance, they need more and more pins,both to handle new features and to provide more and more power to the chip.

Current socket arrangements are often named for the number of pins in the PGA.Commonly used sockets are:

Socket 478 - for older Pentium and Celeron processors

Socket 754 - for AMD Sempron and some AMD Athlon processors

Socket 939 - for newer and faster AMD Athlon processors

Socket AM2 - for the newest AMD Athlon processors

Socket A - for older AMD Athlon processors

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CPU Heatsink with Fan
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A microprocessor can move data from one memory location to another.

A microprocessor can make decisions and jump to a new set of instructions

based on those decisions.

17.Random Access Memory (RAM) - RAM consists of computer chips, which storeinformation. They are installed in rows called banks of nine on the motherboard.

Only 8 chips per row are used to store data while the 9th is used for paritychecking. Data transfer between the CPU and RAM occurs at the fastest possiblerate since it involves no moving parts as do hard and floppy disk drives.

RAM is memory that your computer uses to run programs and softwareapplications on your computer. Without RAM your computer won't function. The

more RAM you have the faster and more smoothly your computer will run.

DIP 16-pin (RAM chip, usually pre-FPRAM)

SIPP (usually FPRAM)

SIMM 30-pin (usually FPRAM)

SIMM 72-pin (so-called "PS/2 SIMM", usually EDO RAM)

DIMM 168-pin (SDRAM)

DIMM 184-pin (DDR SDRAM)

Two Common PC Major RAMs

SRAM Static Random Access Memory- is a type of semiconductor memory. The word "static"

indicates that the memory retains its contents as long as power remains applied,unlike dynamic RAM (DRAM) that needs to be periodically refreshed.

DRAM Dynamic Random Access Memory- Because of this refresh requirement, it is a dynamic memory

as opposed to SRAM and other static memory.

Most commonly used as the main memory is: DRAM

Most Common DRAM used in PCs are:

Synchronous Dynamic RAM (SDRAM)

1. Single Data Rate (SDR) SDRAM is a synchronous form of DRAM.

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2. Double data rate (DDR) SDRAM was a later development of SDRAM, used

in PC memory from 2000 onwards. DDR2 SDRAM is a minor enhancement on DDR-

SDRAM that mainly affords higher clock speeds and somewhat deeper pipelining.

18.Hub or Switch a common connection point of a network

19.LAN Card/Ethernet Card/Network Interface Card (NIC) an expansion card

inserted in the computer to be connected into a network.

20.

20. Router an internetworking devices that passes data packets between networksand makes decision regarding the best path for delivery of data on a network.

21. Networking Media

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Wireless LAN Card

PCI LAN Card

ISA LAN Card

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DeskJet/Inkjet Printer

22. Modems - (which is short for modulator/demodulator) converts the digital data

signal of the PC into the analog data signal that is used on the plain old telephone

system (POTS) which is also called the public telephone switched network (PTSN).

Modems can be installed inside the PC in an expansion slot, or they can beattached to the PC externally through a serial or USB port. An internal modem isinstalled like any other expansion card into a compatible expansion slot.

23.Multimedia Speaker an audio output device

24.Printer an output device that produces paper print outs or hard copies.

25.Web Camera used mostly for video conferencing and to capture still images forprinting and editing.

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UTP Cable (Unshielded Twisted Pair)

Internal ModemExternal Modem

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