Hardware Modules

8/8/2019 Hardware Modules

1/24

What is a Computer?

A machine that can be programmed to :

Receive information.

Process the information according to a set of suitable instructions.

Display desired result information.

A computer can also be used to store information whenever required. It is a device capable of performing arithmetic and logical operations

Computer The Framework

Types of computers

Analog - An analog computer represents data as physical quantities and operates on the data by manipulating the quantities

Digital - A computer that stores data in terms of digits (numbers) and proceeds in discrete steps from one state to the next

Hybrid - Hybrid computers are made by combining features of analog computers and digital computers


2/24

Components of a Computer

Hardware

The physical components of a computer system that can be touched and felt.

E.g. Monitor, keyboard, mouse etc.

Software

A program or set of instructions that enables the computer to perform a specific task.

E.g. Anti-virus, MS Office etc.

Firmware

Firmware is a combination of hardware and software. These are programs that have been written on to the Read-Only Memory (ROM)


3/24

Rear Panel View of a computer Tower


4/24

Switch mode power supply (SMPS) is responsible for converting alternating current( AC) to direct current(DC),filter impurities and split the DC into + and - 5 and 12 V

respectively.

A standard power supply draws power from a local, AC source (usually a wall outlet) and converts it to either 3.3 or 5 volts DC, for on-board electronics, and 12 volts DC

for motors and hard drives. In all cases, it delivers both positive and negative DC to the computer. Power supplies must "condition" the power, smoothing out any radical

changes in its quality. Many homes and offices have power that fluctuates, far more than the delicate parts of a PC can tolerate and survive. Most PC power supplies also

provide the system's cooling and processor fans that keep the machine from overheating.

A power supply converts 110 volt or 220 volt AC current into the DC voltages that a computer needs to operate.

These are as follows:

+3.3 volts DC

+5 volts DC

5 volts DC (ground)

+12 volts DC12 volts DC (ground)

+5 volts DC standby.

The 3.3 volts DC and +5 volts DC standby voltages are used only by ATX motherboards, not AT motherboards.

SMPS

Powersupply connectors

Power supplies use different types of connectors to power the various devices within the computer like Floppy drive power connectors, AT system connectors, ATX power

connectors, and standard peripheral power connectors. Each has a different appearance and way of connecting to the device. Additionally, each type is used for a specific

purpose.

AT system connectors

For AT connector both black (connector) wires need to be connected adjacent to each other.


5/24

Power Supply ConnectorsPower supplies use different types of connectors to power the various devices within the computer Floppy drive power connectors, AT system connectors, ATX powerconnectors, and standard peripheral power connectors. Each has a different appearance and way of connecting to the device. Additionally, each type is used for a specificpurpose.

AT System Connectors

These are two 6-wiresconnectors, labeled P8 and P9. They connect to an AT-only motherboard and deliver the power that feeds the electroniccomponents on it. It is important to note that only computers with AT andbaby AT motherboards use this type of power connector. Most computerstoday use the ATX power connector to provide power to the motherboard.AT connector cointains 6+6 pins. For AT connector both black (connector)

wires need to be connected. If the Mother board uses AT connector, thecomputer will display "It's now safe to turn off the computer".

ATX Power Connector

The ATX system connector (also known as the ATX motherboard power connector)feeds an ATX motherboard. It provides the six voltages required, plus it delivers themall through one connector: a single 20-pin connector. This connector is much easier towork with than the dual connectors of the AT power supply. The computer willautomatically shut down without pressing power button.

Floppy Drive Power Connectors

Floppy drive power connectors are most commonly used to power floppy diskdrives and other small form factor devices. This type of connector is smallerand flatter than any of the other types of power connectors. Theseconnectors are also called Berg connectors.Notice that there are four wires going to this connector. These wires carrythe 2 voltages used by the motors and logic circuits: +5VDC (carried on thered wire) and +12VDC (carried on the yellow wire) plus 2 black groundwires.

Standard Peripheral Power Connector

The standard peripheral power connector is generally used to power different types ofinternal disk drives. This type of connector is also called a Molex connector. This powerconnector, though larger than the floppy drive power connector, uses the same wiring colorcode scheme as the floppy drive connector.


6/24

SATA Power Connector

This connector gives power supply to the SATA devices.

The Motherboard

The spine of the computer is the motherboard, otherwise known as the system board (and less commonly referred to as the planar board). This is an olive green or browncircuit board that lines the bottom of the computer. It is the most important component in the computer because it connects all the other components of a PC together.

On the system board, you will find the following components:

Expansion slots

Memory slots

CPU and processor slots or sockets

Power connectors

On-board disk drive connectors

Keyboard connectors

Peripheral port and connectors

BIOS chip

CMOS battery

Jumpers and DIP switches


7/24

Chipset

A chipset is a collection of chips or circuits that perform interface and peripheral functions for the processor. This collection of chips is usually the circuitry that providesinterfaces for memory, expansion cards, and onboard peripherals, and generally dictates how a motherboard talks to the installed peripherals.

The functions of chipset can be divided into two major functional groups: North bridge and South bridge.

North bridge

The North bridge subset of motherboard chipset includes circuitry or chips that perform one very important function: management of high-speed peripheral communications.The North bridge subset is primarily responsible for AGP communications and processor-to-memory communications. Therefore, much of the true performance of a PC relieson the performance of the North bridge chipset and its communication with the peripherals it controls.

South bridge

The South bridge chipset, as mentioned earlier, is responsible for providing support to the myriad of onboard peripherals (PS/2, parallel, IDE, and so on), managing theircommunications with the rest of the computer and the resources given to them. Most motherboards today have integrated PS/2, USB, parallel, and serial ports.

The South bridge chipset is also responsible for managing communications with the other expansion buses, such as PCI, USB, and legacy buses.


8/24

The Motherboard

Expansion Slots

The most visible parts of any motherboard are the expansion slots. These look like small plastic slots, usually from 3 to 11 inches long and approximately 1/2 inch wide. Astheir name suggests, these slots are used to install various devices in the computer to expand its capabilities. Some expansion devices that might be installed in these slotsinclude video, network, sound, and disk interface cards.

ISA PCI AGP PCI Express

ISA Expansion Slots

The ISA design is one of the most enduring elements of the PC. It can be found onvirtually all systems, from the second-generation IBM PC to machines built today.However, it suffers from two major shortcomings: lack of speed and compatibilityproblems stemming from card design.

Expansion cards must make use of system resources in an orderly way, so that theydo not conflict with other devices. When demands for these system resources are notcoordinated, the system could behave erratically or even fail to boot up. ISA can bean 8 bit slot or a 16 bit slot. It is black in color.

PCI Expansion Slots

The PCI design's special bus and chip set are designed for advanced bus mastering

techniques and full arbitration of the PCI local bus. This allows support of more than

three slots.

The PCI bus has its own set of four interrupts, which are mapped to regular IRQs on

the system. If a PC has more than four PCI slots, some will be sharing interrupts and

IRQs.

The PCI bus allows multiple bus-mastering devices.

Auto configuration lets the PC's BIOS assign the IRQ linking the card to the system

bus. Most PCI cards have no switches or jumpers to set, speeding installation and

preventing many hardware conflicts. It's a 32 bit interface. It is creamy white in

color.


9/24

AGP Expansion Slots

Accelerated Graphics Port (AGP) slots are becoming more popular. In the past, if you

wanted to use a high-speed, accelerated 3D graphics video card, you had to install

the card into an existing PCI or ISA slot. AGP slots were designed to be a direct

connection between the video circuitry and the PC's memory. They are also easily

recognizable, because they are usually brown, are located right next to the PCI slots

on the motherboard, and are shorter than the PCI slots. AGP is dark brown in color

usually. It's a 64 bit interface.

PCI Express

PCI Express or PCIe, (formerly known as 3GIO for 3rd Generation I/O, not to be

mistaken for PCI-X) is an implementation of the PCI computer bus that uses existing

PCI programming concepts.

A connection between any two PCIe devices

is known as a "link", and is built up from a

collection of 1 or more lanes. All devices must

minimally support single-lane (x1) links.

Devices may optionally support wider links

composed of 2, 4, 8, 12, 16, or 32 lanes. This

allows for very good compatibility in two

ways. A PCIe card will physically fit (and work

correctly) in any slot that is at least as large

as it is (e.g. an x1 card will work in an x4 or x16 slot), and a slot of a large physical

size (e.g. x16) can be wired electrically with fewer lanes (e.g. x1 or x8; however it

must still provide the power and ground connections required by the larger physical

slot size). In both cases, the PCIe link will negotiate the highest mutually supported

number of lanes. PCI Express is 64 bit interface.


10/24

Processor Socket and Slot

Sockets and slots on the motherboard are plenty and varied.

Sockets are basically flat and have several rows of holes arranged in a square. Theprocessor slot is another method of connecting a processor to a motherboard, butone into which an Intel Pentium II or Pentium III.

Memory Slots

Memory or random access memory (RAM) slots are the next most prolific slots on amotherboard, and they contain the memory chips. There are varied types of memoryavailable for PCs today. PCs today use memory chips arranged on a small circuitboard.

These circuit boards are called Single Inline Memory Modules (SIMM) or Dual InlineMemory Modules (DIMM), depending on whether there are chips on one side of thecircuit board or on both sides, respectively.

Aside from the difference in chip placement, memory modules also differ in thenumber of conductors, or pins, that the particular memory module uses. Somecommon examples include 30-pin, 72-pin, and 168-pin (the 168-pin modules aremost often DIMM).

Additionally, laptop memory comes in smaller form factors known as Small OutlineDIMM (SODIMM).

The Motherboard

On-Board Floppy and Hard Disk Connectors

These connections are known as drive interfaces and are of two types: floppy driveinterfaces and hard disk interfaces. Floppy disk interfaces allow floppy disk drives tobe connected to the motherboard and, similarly, hard disk interfaces do the samefor hard disks. Most motherboards manufactured today include both the floppy diskand hard disk interfaces embedded on the motherboard.

On Board SATA connector

Serial Advanced Technology Attachment (SATA) is an interface for connecting harddrives to a computer.Unlike IDE which uses parallel signaling, SATA uses serial signaling technology.Because of this the SATA cables are thinner than the ribbon cables used by IDE harddrives. SATA cables can also be longer allowing you to connect to more distantdevices without fear of signal interference. There is also more room to grow with data

transfer speeds starting at 150 MB/s.


11/24

Keyboard Connectors

The most important input device for a PC is the keyboard. All PC motherboards contain a connector that allows a keyboard to be connected directly to the motherboard

through the case. There are two main types of keyboard connectors: AT and PS/2. The AT connector is round, about 1/2 inch in diameter, and has five sockets in the DIN-5

configuration.

The PS/2 connector is smaller and more common than the AT connector. Most new PCs you can purchase today contain a PS/2 keyboard connector as well as a PS/2 mouse

connector right above it on the motherboard.

The Motherboard

Peripheral Ports and Connectors

In order for a computer to be useful and have the utmost functionality, there must be a way for the data to arrive and depart. Many different ports are available for this

purpose.

Briefly, the seven most common types of ports you will see on a computer are serial, parallel, Universal Serial Bus (USB), Video, Ethernet, Sound in/out, and Game ports.

Typical 9-pin and 25-pin serial ports

The above Figure shows an example of the two different types of serial ports: 9-pinmale and 25-pin male.

A Parallel Port

The above Figure shows a typical parallel port (also called a printer port,

because the most common peripheral connected to it is a printer).


12/24

A Universal Serial Bus (USB) Port

Universal Serial Bus (USB) ports look slightly different, as shown in the figureabove.

A Video Port

Video (SVGA) ports (as shown above) are found on motherboards

that have built-in video circuitry to allow the computer to display

images on a monitor. The video port is typically a 15-pin, three row,

female connector.

An Ethernet Port

If your motherboard has an Ethernet network adapter integrated into its circuitry,

you may see an Ethernet port (as shown above), an RJ-45 port, attached to the

motherboard.

A Game Port

The above figure shows an example of a game port (also called a joystick port

because thats the most common device connected to it). Game ports are used to

connect peripheral devices to the computer and use a 15-pin female connector.

Connecting a port to the motherboard with the Dongle Method Peripheral ports Directly Soldered to a Motherboard


13/24

There are two ways of connecting these ports to the motherboard (assuming the

circuitry for providing these functions is integrated into the motherboard). The first,

called a dongle connection, allows you to mount the ports into the computers case

with a special cable (called a dongle). The dongle for each port connects to the

respective pins on the motherboard for that port.

The second method of connecting a peripheral port is known as the direct-solder

method. With this method, the individual ports are soldered directly to the

motherboard. This method is used mostly in integrated motherboards in non-clone

machines. Figure above shows peripheral ports connected to a motherboard with

the direct solder method. Notice that there is no cable between the port and the

motherboard and that the port is part of the motherboard.

Microprocessor

Microprocessor is the brain of any computer that does all the arithmetic computations & logical instructions inside the CPU. Microprocessor also communicates and controlsactivities between all peripherals including hard drive, RAM, multimedia devices and other components of a PC. Microprocessors comprise millions of transistors that contributeto performing additions, subtractions, multiplications, divisions and much more complex instructions.

Initial computing was about using small programs like basic spreadsheets, word processors, simple calculations and some programming. Today's computing requires morepowerful hardware to compete with much powerful programs including complex calculations, graphic designing, gaming, multimedia and much demanding developmentsoftware.

The Factors which affect the performance of a processor are as follows:

Clock Speed

The clock speed is the frequency with which a processor executes instructions. This frequency is measured in millions of cycles per second (megahertz [MHz]) or billions ofcycles per second (gigahertz [GHz]). Generally speaking, the higher the MHz value, the faster the PC.

Cache Memory

Cache memory is a storage area for frequently used data and instructions. It requires a small amount of physical RAM that can keep up with the processor; it uses this RAM

for storage. The processor contains an internal cache controller that integrates the cache with the CPU. The controller stores frequently accessed RAM locations to providefaster execution of data and instructions. This type of cache is known as a level 1(L1) cache.

L1 Cache L2 Cache L3 Cache

In addition to external memory (RAM) will improvethe performance as it is much faster than RAM, foundintegrated along with the processor.

In addition to L1 Cache & DRAM, it was available onthe motherboard earlier and now "in-built" today inmost of the processors.

In addition to L1 and L2 Cache, available in recentprocessor Intel Pentium IV HT Extreme edition,improves performance much better.


14/24

Microprocessor

The Bus

The processors ability to communicate with the rest of the systems components relies on the supporting circuitry. The system boards underlying circuitry is called the bus.The computers bus moves information into and out of the processor and other devices, allowing all the devices to communicate with each other. The bus consists of severalcomponents, including the external bus, the data bus and the address bus.

The External Bus (System Bus)

The external bus is also referred to as the system bus or expansion bus. Theexpansion bus is a bus system that allows the processor to talk to another device. Itis known as an external bus system because it is outside the processor. The devicesare connected through expansion cards and slots. An expansion card is a removablecircuit board that expands the capability of the computer.

The Data Bus

The data bus is used to send and receive data. The larger the bus width, the moredata that can be transmitted (and, therefore, the faster the bus).

Data in a computer is transferred digitally. A single wire carries +3.3V or +5V toindicate a 1 data bit; it carries 0 volts to indicate a 0 data bit. (Remember, computersuse the binary system to transmit information.) The greater number of wires allowsmore bits to be transmitted simultaneously.

For example, a 16-bit data bus width has 16 wires to transmit data, and a 32-bit datachip can transmit twice the amount of data as a 16-bit chip. A good comparison isthe highway system. A single traffic lane allows only one car through at a time,whereas two lanes allow twice the amount of traffic to pass.

The Address Bus

The address bus contains a set of wires to carry information into and out of theprocessor.The information the address bus sends used to describe memory locations.These locations are used for data being sent or retrieved. The address bus carries asingle bit of information, representing a digit in the address, along each wire. Thesize of the address bus corresponds to the number of address locations. The largerthe address bus, the more memory address locations can be supported. The morememory address locations a processor can address, the more RAM a processor can

use.

Bus Speed

Motherboards are designed to be more or less universal. They have a processorsocket or slot that can support many different processor types and speeds. Thespeed of the bus and the speed of the processor are directly related. Typically, thebus speed is set to 66MHz, 100MHz, or 133MHz plus a multiplier. For example, if youhave a 450MHz processor, you set the processor speed jumper to 450MHz, theexpansion bus speed to 100MHz, and the multiplier to 4.5 (4.5 100MHz =450MHz). Speeds for processors below 200MHz are generally set without a multiplier.


15/24

Memory

Memory is the electronic holding place for instructions and data that your computer's microprocessor can reach quickly.When your computer is in normal operation ,its

memory usually contains the main parts of the operating system and some or all of the application programs and related data that are being used. Memory is often used as a

shorter synonym for Random Access Memory(RAM).

There are two major classes of computer memory:

Non - Volatile

The Memory is said to be Non Volatile, if the data is retained even though the powerto the computer is shut off. The setup data held in CMOS (complementary metal-oxide semiconductor), is a good example of nonvolatile memory.

Volatile

The memory is said to be Volatile, if the data is lost when the computer loses the

power. The RAM is an volatile memory

The various types of Non-Volatile Memory are as follows:

ROM

ROM stands for Read-Only Memory. It is called read-only because it cannot bewritten to. Once information has been written to the ROM, it cannot be changed.ROM is normally used to store the computers BIOS, because this informationnormally does not change.

CMOS

CMOS is a special kind of memory that holds the BIOS configuration settings. CMOS

memory is powered by a small battery so the settings are retained when the

computer is shut off. The BIOS reads information such as the hard drive types which

are configured for this computer to use, the drive(s) it should search for boot sectors,

and so on. CMOS memory is usually not upgradable in terms of its capacity.

RAM

RAM (Random Access Memory) is most often referred to when PC memory is discussed. RAM is the form of volatile memory used to hold temporary instructions and datafor manipulation while the system is running. The term random is applied because the CPU can access or place data to and from any addressable RAM on the system. Ifpower to the system is lost, all RAM is lost as well.

Input Devices

Lets start this chapter off by talking about some of the most commonly used peripheral devices: input devices. As their name suggests, input devices exist so that humanbeings can communicate with the object we call a computer. These devices interpret the intentions of their users (via a keystroke or some other movement) to tell thecomputer to perform some action. Without them, the computer would be of little use to us.


16/24

Keyboard

The most common PC input device is the keyboard. This type of device translates keystrokes into letters or

numbers. The letters are then interpreted and commands are performed, depending on what is being sent.

Input Devices

Mouse

A mouse is an input device which allows the user to control a cursor to manipulate data without complicated commands. The mouse or mice was invented by Douglas

Englebart in 1963, who at the time was working at the Stanford Research Institute. Today the mouse are now found on every Apple and PC computer and used withvarious different GUIs.

Types of Mouse and its Technologies

Mechanical Mice

Mechanical Mice requires that the mouse be set on a flat surface. The distance andthe speed of the rollers inside the mouse determines how far the mouse cursormoves on the screen depending on the software configuration.

Optical Mice

Optical Micerequire a special mouse pad which has a grid pattern. A sensor insidethe mouse determines the movement by reading the grid as the mouse passes overit while emitting a light from an LED or sometimes a laser. This type of mouse ismuch more accurate than the ordinary optical mechanical mouse which relies on thetraction between the mouse ball and the rollers. One drawback to an optical mouseis they can have problems in bright lights.New Optical Mice no longer have the disadvantages of earlier mice and are capableof being utilized on any surface. In comparison to the traditional Optical-Mechanical

mouse the Optical is a much better solution for a computer mouse.


17/24

Optical Storage Device

CD-ROM Drives

A CD- ROM (CD-ROM stands for Compact DiscRead-Only Memory) is an optical storage device which is accommodated by a CD-

ROM drive.These drives are slightly different from other storage media in several ways. First, they read information differently than

magnetic media disk drives do. CD-ROM drives use laser light to read the information from the media, they are described as optical

drives.

Another difference between magnetic media and CD-ROM drives is that CD-ROM drives are read-only devices ( Compact DiscRead-

Only Memory). The only way to write to a CD-ROM is during manufacture time, when the pits are burned into the substrate of the

disc. Once written, they cannot be erased.Today, using the latest writable and re-writable CDs we can write new data as well as

erase existing and re-write new data.

When reading information from a CD, the drive basically reads a lot of pits and lands (lands are the spaces between the pits) in the disc surface. The pits are etched into

the CD at production time. The laser reflects off the CDs surface and onto a sensor. The sensor detects the pattern of pits and lands as the disc rotates and translates them

into patterns of 1s and 0s. This binary information is fed to the computer that is retrieving the data.

A CD-ROM disc has a single track that runs from the center to the outside edge, exactly the reverse of the groove on a record. A CD-ROM uses basically the same

technology as the audio compact discs used in most homes today. When a CD-ROM is placed into a CD-ROM drive, a motor spins the CD at a specific rate. A laser that

reads the CD is then activated.Due to these basic similarities, several compatibilities exist between the different compact disc technologies. For example, it is possible to

play audio CDs in a computers CD-ROM drive. Also, some computer CDs have audio tracks on them and are made to be used in either type of CD drive (home audio or

computer).

Storage Devices

Floppy Disk Drives

The floppy disk drive is the most commonly used magnetic storage device. Floppy disks have only one platter encased in a plas tic

shell and are available in different capacities.

A floppy drive has either one or two read/write heads. Each head moves in a straight line on a track over the disk rather than on an

angular path as with fixed disk systems. When the disk is placed into the drive, a motor engages the center of the disk and rotates

it in 3600RPMs speed. This action moves the tracks past the read/write heads.


18/24

Storage Devices

Magnetic Storage Device

Disk Drives

A disk drive is an encasement which accommodates a disk and helps to read and write data on the disk .There are different types of disk drives for different types of disks:- Hard disk drive ( HDD )- Floppy disk drive ( FDD )

Hard Disk DrivesHard disks actually contain several disks called platters, stacked together and mounted through their centers on a small rod called aspindle. The disks are rotated about this rod at a speed between 2,000 and 10,000 revolutions per minute (RPM). As the disksrotate, one or more read/write heads float approximately 10 micro inches (about one-tenth the width of a human hair) above thedisk surfaces and make, modify, or sense changes in the magnetic positions of the coatings on the disks. Several heads are movedtogether as one unit by an actuator arm. There is usually one head for each side of a platter.

This entire mechanism is enclosed in a hard disk case. These disks are also called fixed disks because the mechanism is notdesigned to be removed. The disk platters, though perfectly free to revolve at high RPM, are otherwise fixed in place.

SATA


19/24

Ports and Connectors

A port is a place where data arrives or departs in a computer .There are two types of ports:

- Physical ports - Eg. Serial, parallel, game and USB.

Peripheral Port Connector Types

DB-Series

DB connectors, the most common style of connector found on computers today, are typically designated with DB-n, wherethe letter n is replaced by the number of connectors. DB connectors are usually shaped like a trapezoid.

The nice part about these connectors is that only one orientation is possible. If you try to connect them upside down ortry to connect a male connector to another male connector, they just wont go together, and the connection cant bemade.

RJ-Series

Registered Jack (RJ) connectors are most often used in telecommunications. Figure shows the two most commonexamples of RJ ports and connectors: RJ-11 and RJ-45. RJ-11 connectors are used most often in telephone hookups; yourhome phone jack is probably an RJ-11 jack or port. RJ-45 connectors, on the other hand, are most commonly found onEthernet networks that use twisted pair cabling.

On the left in this picture is an RJ-11 connector and on the right is an RJ-45 connector. Notice the size difference.

As you can see, RJ connectors are typically square with multiple gold contacts on the top (flat) side. A small locking tab onthe bottom prevents the connector and cable from falling or being pulled out of the jack accidentally.


20/24

Ports and Cables

Universal Serial Bus (USB)

Most computers built after 1997 have one or two flat ports in place of one DB-9serial port. These ports are Universal Serial Bus (USB) ports, and they are used forconnecting multiple (upto 127) peripherals to one computer through a single port(and use of multi port peripheral hubs). USB version 1.1 supported data rates ashigh as 12Mbps (1.5MBps). The newest version, USB 2.0, supports data rates ashigh as 480Mbps (60MBps).

Because of USBs higher transfer rate, flexibility, and ease of use, most devices thatin the past used serial interfaces now come with USB interfaces.

Infrared

Increasing numbers of people are getting fed up with being tethered to theircomputers by cords. As a result, many computers (especially portable computingdevices like laptops and PDAs) are now using infrared ports to send and receivedata. An infrared port is a small port on the computer that allows data to be sentand received using electromagnetic radiation in the infrared band. The infrared portitself is a small, dark square of plastic (usually a very dark maroon) and cantypically be found on the front of a PC or on the side of a laptop or portable.

Centronics

The last type of port connector is the Centronics connector. It has a unique shape.It consists of a central connection bar surrounding by an outer shielding ring. TheCentronics connector is primarily used in parallel printer connections and SCSIinterfaces. It is most often found on peripherals, not on computers themselves(except in the case of some older SCSI interface cards).


21/24

PS/2 (Keyboard and Mouse)

A PS/2 port (also known as a mini- DIN 6 connector) is a mouse and keyboard

interface port first found on the IBM PS/2. It is smaller than previous interfaces

(the DIN-5 keyboard port and serial mouse connector), and thus its popularity

increased quickly. You can tell the difference because usually the keyboard port is

purple and the mouse port is green. Also, typically there are small graphics of a

keyboard and mouse, respectively, imprinted next to the ports.

VGA port

The last type of port connector is the Centronics connector. It has a unique shape.It consists of a central connection bar surrounding by an outer shielding ring. TheCentronics connector is primarily used in parallel printer connections and SCSIinterfaces. It is most often found on peripherals, not on computers themselves(except in the case of some older SCSI interface cards).

BIOS ( Also known as ROM BIOS and Firmware ) and CMOS

BIOS stands for Basic Input/Output System. The BIOS communicates between the computer and devices. The BIOS is usually stored in ROM. It was created by IBM to actas a translator to run the same operating systems on different hardware platforms. When the operating system needs to access a piece of hardware, it would now ask theBIOS, rather than just taking control of the hardware. The use of BIOS prevented programs from fighting over hardware. As long as the operating system (such as DOS)uses the BIOS for its hardware requests, it can run on different hardware platforms. The BIOS creates a standard reference point for many different types of hardware.

BIOS Chip

Aside from the processor, the most important chip on the motherboard is the basic input/output system (BIOS) chip. This special

memory chip contains the BIOS software that tells the processor how to interact with the rest of the hardware in the computer. The

BIOS chip is easily identified: If you have a non-clone computer (Compaq, IBM, HP, and so on), this chip has on it the name of the

manufacturer and usually the word BIOS. For example, the BIOS chip for a Compaq has something like Compaq BIOS printed on it.

For clones, the chip usually has a sticker or printing on it .

Flashing : Process of upgrading BIOS.


22/24

CMOS

CMOS (Complementary Metal Oxide Semiconductor) contains settings that determine how the computer is configured. These settings are user-configurable and can beaccessed through the CMOS setup program by pressing some key combination at startup (such as Shift+F1 or Ctrl+Shift+Esc). For example, one setting in CMOS controlsthe boot sequence. The parameter is usually called boot sequenceand can be set to either A: C: or C: A: (in most cases). Every CMOS setup program is different anduses different commands for configuration. Usually, though, the CMOS setup program is menu driven and will present you with a list of settings that you can configure, aswell as the possible settings for them. When youre done configuring, you can press Esc and the CMOS setup program will ask you to press Enter to save the changes andreboot. After rebooting, the computer will operate with the modified settings.

Your PC has to keep certain settings when its turned off and its power cord is unplugged. Some of these settings include:Date

Time

Hard drive configuration

MemoryYour PC keeps these settings in a special memory chip called the Complimentary Metal-Oxide Semiconductor (CMOS RAM ) chip.

CMOS Battery

To maintain CMOS RAM settings, it is essential to have power constantly. When you shut down the computer and it stops receiving

power supply , CMOS battery continues to provide power supply to CMOS RAM to main its contents.

Monitors

Is bigger and bulkier when compared to the more modern flat screensConsumes more power when compared to flat screens A beam of electrons

lights up pixels on the screen.

Consumes less power and occupies less space, owing to its flat natureReflective twisted pneumatic liquid crystal display Commonly used in

notebooks, mobile phones, calculators etc.


23/24

Printers

Printers are considered standard PC components; they are often bundled with computers and sold to consumers as part of a complete package. The most common add-

ons, printers are manufactured in several popular forms. Like other devices, each type has unique advantages and disadvantages.

A printer is a device that prints text or illustrations on paper, transparent sheets, etc

Three of the most commonly used printers are

Dot matrix

Ink jet

Laser jet

Dot-Matrix Printers

A quick trip through a consumer electronics store might lead the average person tobelieve the age of the dot-matrix printer is over. The home and home officesegments of the market are now the domain of the ink-jet and low-cost laserproducts. Still, in business locations, where the ability to print several copies atonce is a driving factor, the loud and lowly dot-matrix still rules.

Ink-Jet Printers

Ink-jet printers spray ink onto paper to form images. They produce good-qualityprinting andcompared to dot-matrix and wax printersthey are relatively fast.They also require little maintenance beyond cleaning and ink cartridge replacement.Their ability to easily produce color as well as standard black-and-white imagesmakes them attractive.


24/24

Laser Printers

The laser printer has become the dominant form of computer output device, with models ranging from personal, low-volume,desktop printers to behemoths that fill half a room and serve hundreds of users, churning out reams of pages every day.

All laser printers follow one basic engine design, similar to the one used in most office copiers. They are non impact devices thatprecisely place a fine plastic powder (the toner) on paper. Although they cost more to purchase than most ink-jet printers, theyare much cheaper to operate per page, and the "ink" is permanent.

Printer Connection

There are eight major Printer connection types: serial, parallel, Universal Serial Bus (USB), network, infrared, SCSI, IEEE 1394, and wireless. Youve learned about theseconnections earlier, but now you will learn how they apply to printers.

Parallel

When a printer uses parallel communication, it is receiving data eight bits at a timeover eight separate wires (one for each bit). Parallel communication is the mostpopular way of communicating from computer to printer, mainly becaus e its fasterthan serial.

A parallel cable consists of a male DB-25 connector that connects to the computerand a male 36-pin Centronics connector that connects to the printer. Most of thecables are less than 10 feet long.

Universal Serial Bus (USB)

The most popular type of printer interface as this book is being written is the

Universal Serial Bus (USB). In fact, it is the most popular interface for just aboutevery peripheral. The convenience for printers is that it has a higher transfer ratethan either serial or parallel and it automatically recognizes new devices.

Network

Some of the newer printers (primarily laser and LED printers) have a special

interface that allows them to be hooked directly to a network. These printers have anetwork interface card (NIC) and ROM-based software that allow them tocommunicate with networks, servers, and workstations.

The type of network interface used on the printer depends on the type of networkthe printer is being attached to. For example, if youre using a Token Ring network,the printer should have a Token Ring interface.

Documents

Hardware Modules