Chapter-I

TYPICAL CONFIGURATION OF COMPUTER SYSTEM

What is the motherboard?

The motherboard is the main circuit board of the computer which

contains the processor, memory, expansion slots, bus and other
components.

Or

A Printed Circuit Board (PCB) used to connect all the system

components like CPU, RAM, expansion slots and other components.

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Explain three types of the motherboard.

There are four different types of the mother board. They are as follows.

1. XT - Motherboard.
2. AT Motherboard.
3. Baby AT Motherboard.
4. ATX Motherboard.

XT - Motherboard: XT Stands for Extended Technology They are old

model motherboards. In this we will find old model processor socket
like LIF (Low insertion force) sockets, RAM slots like DIMM [Dual inline
memory modules] and ISA [Industry standards architecture].They
have 12 pin power connector and no ports.

Example: Pentium - I, Pentium –II, Pentium MMX and Pentium –II

processors.

2. AT- Motherboard

Advanced Technology AT Motherboards have PGA (Pin grid array)

sockets SD. RAM Slots 20 Pin power connector PCI and ISA slots Its

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size is 12' wide X 13.8' deep AT has 5 Pin large keyboard connector.
Example PENTIUM III Processors.

3 Baby -AT Motherboard:

It is the combination of XT and AT motherboard SDRAM and DDRRAM,

ISA, PCI slots are present. It has 20 Pin Power connector.

Example: Pentium III, Pentium IV.

SDRAM: Synchronous Dynamic Random Access Memory

DDRRAM: Double Data Rate Random Access Memory

4 ATX -Motherboard :

Advanced technology extended. It has MPGA processor socket, DDRAM

PCI slots, AGP slots, SATA connectors. IDE interfaces. 20 pin and 24 pin
ATX connectors and ports. Its size is 9.6" X 9.6'. Latest motherboards all
are called as ATX motherboards.

Example: Pentium IV, Dual-core, Core2 DUO.Quad core,i3,i5 and i7

processors.

SATA: Serial Advanced Tech Attachment.

IDE: Integrated Drive Electronics.

Explain the characteristics of the motherboard

The motherboard may be characterized by the form factor, chipset and

type of processor socket used.

Characteristics of the Motherboard:

The form factor: is the specification of a motherboard – It explains the

dimensions,

Power supply: type, location of mounting holes, number of ports on the

back panel, etc.,

A Chipset is a collection of microchips (such as CPU, BIOS, memory,

mass storage, interfaces, controllers and input-output devices)

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designed with built-in circuits on the motherboard to work together to
perform specific functions.

Processor socket: It is a place where the CPU is connected. It is designed

as per the compatibility.

What is cache memory? Explain their types.

Cache memory is a high-speed memory placed in between RAM and

CPU to speed up the processing of CPU.

Types of cache memory

L1, L2 and L3 are the three types of cache memory.

L1 cache is extremely faster but relatively smaller. Its size varies from
32KB to 51KB.

L2 cache is extremely slow but relatively larger. Its size varies from
1MB to 2MB

L3 cache is specialized cache memory used to speed up the L1 and L2

and located on the motherboard.

Power Supply:

Power Supply to a Computer System Electric power is the main source

of supply for the operation of electronic components of a computer.
Therefore continuous power supply is essential for the computer to
prevent them from failures, breakdown or shutdown. All computers
come with a power supply.

There are two types of power supply connected to a computer system.

They are, Switch Mode Power Supply (SMPS) and Uninterruptable
Power Supply (UPS).

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SMPS: An SMPS converts AC power from an electrical outlet to the DC
power needed by system
components. An SMPS is a
metal box in the rear of the
system that is attached to the
computer chassis and to the
system board. The power
supply contains the power card
plug and a fan for cooling,
because it generates a lot of
heat. An SMPS with a rating of more than 300 watts is needed In a PC
the SMPS converts 230 volts of AC to 5 to 12 DC volts and the wattage is
around 180 to 300 watts, 450 watts and 500 watts.

What is the function of the UPS? Mention different types of UPS.

UPS means uninterrupted power supply. When Power supply failure

occurs, UPS will supply power with the help of the battery for a
specified number of hours depending on the battery capacity.

Types of UPS

The different types the UPS are:

 Online UPS,
 Off-line UPS.

Explain the types of UPS.

Online UPS: The inverter is directly connected to the device and it is

always on to give the required power to the device. If power fails, the
battery backup circuit switches on and takes the load. It is very costly.

Offline/Standby UPS: Stand by UPS monitors the power supply and

switches to battery power as soon as a power failure to give AC power
to the device.

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Processors (CPU):

 The processor or CPU is the main component on the motherboard

and is called the brain of the computer.
 The CPU consists of Arithmetic Logic Unit (ALU) and Control Unit
(CU) and registers.
 Arithmetic Logic Unit (ALU) performs all the arithmetic and logic
operations on data.
 CU is responsible for organising the processing of data and
instructions.
 Registers which are temporary storage areas for holding data,
and instructions.

Clock Speed: A measure of a processor’s operating speed, currently

measured in MHz (Megahertz)GHz(Gigahertz) .

A CPU’s performance is measured by the number of instructions

executed per second, i.e. MIPS or BIPS. PCs presently come with a
clock speed of more than1GHz.

Microprocessor: It is an integrated circuit that contains all the

functions of a CPU of a computer.

This tiny chip contains the entire computation engine. Examples Intel
,AMD,Celeron.

BIOS (Basic Input Output System) BIOS is a small chip on the

motherboard that holds a set of instructions to load the hardware
settings required to activate various devices like keyboards, monitors
or disk drives.

 The BIOS runs when the computer is switched ON.

 It performs a Power On self-test (POST)
 It checks if the hardware devices are present and functioning
properly.
 BIOS invoke the bootstrap loader to load the Operating system
into memory.

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CMOS (Complementary Metal Oxide Semiconductor) CMOS is a type of
memory chip to store the date, time and system setup parameters.
These parameters are loaded every time the computer is started.

That is why we observe when the

computer is turned ON, the system still
displays the correct clock time. BIOS, as
well as CMOS, are kept powered by a small
lithium-Ion battery located on the
motherboard. It can be seen in the figure.

What is meant by Slot? Explain any three

types of Slots

Slots: A slot is an opening in a computer where you can insert a printed

circuit board. Slots are often called expansion slots because they allow
you to expand the capabilities of a computer.

Expansion Slots These slots are located on the motherboard. The

expansion cards are inserted in the expansion slots. These cards give
the computer new features or increased performance. There are
several types of slots:

ISA (Industry Standard Architecture) slot – ISA slot is used to connect

modem and input devices.

PCI (Peripheral Component Inter-Connect) slot – PCI slots are used to

connect graphics accelerator cards,
sound cards, internal modems or SCSI
cards. They are much faster than ISA
cards.

AGP (Accelerated Graphic Port) slot – AGP

slot is meant to provide faster access to a

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graphics accelerator card, thus enhancing the visual experience for the
user. All Celeron and Pentium-III motherboards come with an AGP slot.

RAM slot – RAM slot is used to install memory and is

of two types. They are SIMM (Single Inline Memory
Module) slot and DIMM (Dual Inline Memory Module)
slot. The original Pentium systems typically have
either four 72-pin SIMM slots or two 168-pin DIMM
slot to install the memory.

Processor slot – Processor slot is

used to insert the processor chip
which is the largest chip on the
motherboard. It can be identified, as
a heat sink or fan is located on top of
it.

PCI Express slot – It has faster bus architecture than AGP and PCI
buses.

PC Card – It is used in laptop computers. It includes Wi-Fi card,

network card and external modem.

What is meant by Port? Explain any two types of Ports.

The ports and interfaces are used to

connect external devices like printers,
keyboards or scanners to the computer,
which gets connected to the computer’s
motherboard.

These ports and interfaces are found on

the rear side of a computer. There are
several types of ports like serial port,

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parallel port, USB port, and AGP port etc. which is given

Serial port: Serial port is also known as communication (COM) ports or

RS232-c ports. They are used for
connecting communication devices like
mouse and modem. This port transfers
data serially one bit at a time. It needs a
single wire to transmit 1 bit of data. Hence
it takes 8 times longer to transfer a byte.
There are two varieties of Com ports, the 9-pin ports and 25-pin ports.

Parallel port: Parallel ports are used to connect external input/output

devices like printers or scanners. This port facilitates the parallel
transfer of data, usually one byte (8-bits) at a time. Parallel ports come
in the form of 25-pin connector

IDE (Integrated Digital Electronics) port IDE devices like CD-ROM drives
or hard disk drives are connected to the motherboard through the IDE
port.

USB (Universal Serial Bus) port USB port gives a

single, standardized, easy-to-use way to connect a
variety of newer peripherals to a computer. These
devices include printers, scanners, digital cameras,
web cameras, speakers etc., USB supports a data
speed of 12 megabits per second, supporting up to 127
devices. USB is a plug- and-play interface between a
computer and add-on devices. i.e. a new device can be
added to the computer without adding an adapter card
or even turning the computer off.

PS-2 port (Personal System-2 port)

The PS-2 port was developed by IBM to interface keyboards and

pointing devices like mouse, trackballs and touch pads. This port is also
called as mouse port as most computers now have a PS-2 port to

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connect a mouse. This port uses synchronous serial signals to
communicate between the keyboard and a mouse to the computer.

AGP (Accelerated Graphics Port) port

The AGP port is used to connect to graphic

card that provides high-speed video
performance typically required in games
and other multimedia applications.

SCSI (Small Computer System Interface) port

This port is used for adding external devices

such as high-speed Hard disks, high-end
scanners and CD-ROM drives. It does fast
data transfers and I-O operations. These
ports are expensive, as they provide faster
access at very high speeds and need separate
dedicated adapters to function

VGA (Visual Graphics Adaptor) port

Connects monitor to a computer’s video card.

It has 15 holes and is similar to serial port
connector, but serial port connector has
pins, this has holes.

Power Connector

Has three-pronged plug. It connects to the computer’s power cable that

plugs into a power bar or wall socket.

Fire wire Port

Transfer large amounts of data at very fast

speed. It connects camcorders and video
equipment’s to the computer. The data travels at

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400 to 800 megabits per second. It is invented by Apple. The three
variants of fire wire port are 4-Pin fire wire 400 connector, 6-Pin fire
wire 400 connector and 9-Pin fire wire 800 connector.

Modem (Modulator demodulator) connects a PC’s

modem to the telephone network.

Ethernet Port

Connects to a network and high speed Internet it

connects network cable to a computer. This port resides
on an Ethernet Card. Data travels at 10 megabits to 1000
megabits per second depending upon the network
bandwidth.

Game Port connects a PC to a joystick. It is now replaced by USB.

DVI (Digital Video Interface) port connects a Flat panel LCD monitor to
the computer’s high-end video graphic cards. It is very popular among
video card manufacturers.

Disk Controllers

Disk controller is the circuit that enables the CPU to communicate with
a hard disk, floppy disk or other kind of disk drive. Modern disk
controllers are integrated into the disk drive.

Hard disk controller (HDC) The hard disk

controller is the interface that enables the
computer to read and write information to
the hard drive. This connector is used to
insert an IDE (integrated Digital
Electronics).This drive is attached to the
motherboard by means of 40-wire ribbon cable.
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 Floppy disk controller (FDC) A Floppy-disk
controller is the interface that directs and
controls reading from and writing to a
computer’s floppy disk drive (FDD).

The floppy disk controller usually

performs data transmission in direct memory access (DMA) mode. A
single floppy-disk controller board supports a 33-wire ribbon cable and
can connect up to four floppy disk drives to the motherboard.

Primary memory

Primary memory is also known as main memory. This memory is of two

types: Random Access Memory (RAM) and Read Only Memory (ROM)

RAM temporarily stores the computer’s operating system, application

programs and current data so that the
processor can reach them quickly. RAM is
a faster memory and volatile in nature. i.e.
when the power is switched off, the data in this memory is lost.

ROM is a small memory, which

stores the boot firmware (called
BIOS). BIOS hold enough
information to enable the
computer to check its hardware
and load its operating system into its RAM at the time of system
booting. ROM is non-volatile in nature. i.e., even when the computer is
switched off, the contents of ROM remains available.

Types of RAM

There are different types of RAM, depending on the technology used to

construct a RAM. Some of the common types are:

DRAM or Dynamic RAM is the most

common type of memory chip. DRAM is
mostly used as main memory, since it is
small and cheap. It uses transistors and

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capacitors. The transistors are arranged in a matrix of rows and
columns.

The capacitor holds the bits of information 0 and 1. The transistor and
capacitor are paired to make a memory cell. The transistor acts as a
switch that lets the control circuitry on the memory chip read the
capacitor or change its state.

DRAM must be refreshed continually to store information; otherwise it

will lose what it is holding. The refresh operation occurs automatically
thousands of times per second. DRAM is slow because the refreshing
takes time. Access speed of DRAM ranges from 50 to 150 ns. [Nano
Seconds]

SRAM or Static Random Access memory

chip is usually used in cache memory due to
its high speed. SRAM uses multiple
transistors (4 to 6), for each memory cell. It
does not have a capacitor in each cell. A
SRAM memory cell has more parts, so it takes more space on a chip
than DRAM cell. It does not need constant refreshing and therefore is
faster than DRAM.

SRAM is more expensive than DRAM, and it takes up more space. It

stores information as long as it is supplied with power. SRAM is very
fast and easier to use. The access speed of SRAM ranges from 2 to
10ns.

SDRAM or Synchronous Dynamic Random

Access Memory is a special type of DRAM that
is synchronized to the system clock. Since it is
synchronized to the CPU, it knows when the next cycle is coming, and
has the data ready when the CPU requests it. This increases efficiency
by reducing CPU waiting time.

DDR-SDRAM or Double-Data Rate SDRAM works the same way as does

ordinary SDRAM. Data transfer rate is double when compared to
SDRAM.

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What is meant by BUS? Explain about BUS with neat diagram.

A bus is a collection of parallel wires that form a pathway to carry

address, data and control signals.

The functional features of a bus are:

 A bus is a set of wires and each wire can carry one bit of data.
 A bus width is defined by the number of wires in the bus.

A computer bus can be divided into two types:

Internal Bus:

 The Internal bus connects major computer components like

processor, memory and I/O.
 It is also called as System bus.

External Bus.

 It connects the different external devices, peripherals, expansion

slots, I/O ports and drive connections to the rest of a computer.
 It is also called an Expansion bus and is slower than the system
bus.

A system bus or expansion bus comprises of three kinds of buses:

1. Data bus.
2. Address bus.
3. Control bus.

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Data Bus:

 It provides a path to transfer data between CPU and memory.

 The data bus may consist of 32, 64, 128 lines of wire.
 The bus speed is measured in MHz and higher the bus speed,
faster the processer speed.

Address Bus:

 It connects CPU and RAM with a set of lines of wire similar to a

data bus.
 The address bus width determines the maximum number of
memory locations the computer can address.

Control Bus:

 It is used to control the access to and the use of the data and
address lines.

Explain the components of a Motherboard?

Bus: It is a collection of wire which carries information between

different components of a computer.

I/O ports and interfaces: The ports are the connector available at the
backside of the computer interface is an electronic circuit used to
interconnect I/O devices to a computer’s CPU or memory.

Disk Controllers: The disk controller is the circuit the enable the CPU to
communicate with the hard disk, floppy disk and other types of disk
drives.

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CMOS: It is a memory chip used to store date, time and system
parameters. Small Lithium-Ion battery is used to the power supply to
CMOS and BIOS.

Slots: A slot is a socket in the motherboard which is used to connect the

add on card.

General Structure of Motherboard

 The primary function of the processor is to execute the
instructions given to it and produce the results.
 If fetches instructions and data from the primary memory and
performs the required operations.
 North Bridge and South Bridge are two chips in core logic chipset on
the PC motherboard.
 North Bridge or north chipset is responsible for the control of high-
speed components like CPU, RAM, Chipset, BUS speed control and
switch control data, ensuring data back and forth between the
components in a smooth and continuous, fully exploit the speed of
the CPU and RAM.
 SouthBridge or south chipset is similar to a north chipset, but the
southbridge driver chipset components slower as Sound Card,
Net Card, hard disk, etc.

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