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Components of System Unit

Internal Power Supply (SMPS)

Exhaust Fan

Speaker

Motherboard

Microprocessor

Storage Systems

SMPS (Switch Mode Power Supply)

The system draws power from AC mains through a power protection device. This power is not directly supplied to the internal components, instead one of

the components called Internal Power Supply.

Otherwise known as Switched Mode Power Supply. It can convert the AC input into DC output of 5 & 12 volts.

Fig : SMPS

SMPS

Controller Cables

RAM (storage)

Floppy Disk

Drive

Speaker

Motherboard

Hard Disk Drive

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Exhaust Fan

The SMPS has a small fan, called exhaust fan, attached to it. It can rotate as long as the system switched on.

Main function is – cool the SMPS Unit

Fig :Exhaust Fan

Speaker The system unit has also a small audio speaker attached to it. It is connected with the Motherboard.

It can create a beep sound to indicate everything is working satisfactory. Also used to entertainment programs to produced sound effects.

Fig :Speaker

Motherboard

When you open the system unit, a large board containing a number of tiny

electronic circuits called Motherboard.

All PC peripheral devices are connected with the Motherboard.

Fig :Motherboard

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The components of the motherboard are:

Chipset

Microprocessor Clock chip Memory—RAM and ROM

Bus Ports

Chipset

Is a series of chips attached directly to the motherboard

Controls the system and its capabilities.

Is soldered onto the motherboard and is not upgradeable without a new motherboard.

Each device attached to the motherboard has different chipset.

Example: Pentium III and Pentium IV

Microprocessor The microprocessor consists of ALU Unit, Control Unit, Memory unit (Register).

The microprocessor controls the activities of the various components of the

computer and also responds to requests from the peripheral devices.

The microprocessor can perform mathematical operations like addition,

subtraction, multiplication and division using ALU.

It can move data from one memory location to another

The capacity of Microprocessor is measured in the term of the number of bits it

can send or receive & the number of bits it can process internally.

Ex – 8088 --- 8 / 16 bit processor

80286 – 16 / 16 bit processor

Manufacture company – Intel , Motorola

Pentium is a 32 bit processor

Pentium IV is a 32 bit processor with 64 data path.

Fig :Microprocessor

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Clock chip

Provides the timing signal in the form of electronic pulses that

are used by the computer components to set up a working

pace.

Bus

Bus is a set of wires inside the motherboard.

Connects the microprocessor to other devices.

Comprising a set of 8 wires for carrying data is called the data bus.

Ports

Ports are inlets and outlets of the PC.

Ex - Parallel Port Standard, Serial Port Standard, USB Port, Audio Port,

Infrared Port.

Storage Device/Media

Data needs to be stored for later use on storage media.

The two types of storage media are: Primary storage media Secondary storage media

Primary storage media

Primary memory is called the main memory of a computer system. It is the internal storage area of the machine.

Random Access Memory (RAM) This is the memory that the computer uses for storing the programs and

their data while working on them.

RAM has the following characteristics:

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Data within the RAM can be read or modified, i.e. you can either read

from the RAM or write onto it. Hence it is called read/write memory

Fig: Random Access Memory (RAM)

ROM (Read Only Memory)

It is internal permanent storage memory.

ROM contains permanently recorded machine level instructions that are vital

for starting the computer.

One set of instruction in ROM is called the ROM-BIOS

All machine-level instructions are stored in the ROM.

Secondary storage media

Compact Disk (CD)

DVD (Digital Versatile Disc or Digital Video Disc )

Floppy Disk

Cartridge Tape

Magneto-Optical Disk

USB drive / Pen Drive

Memory Stick

Hard Disk

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Picture of some Permanent Storage Memory

Permanent Storage Memory

Hard Disk:

Data store permanently Size may be 160GB, 320GB, 500GB, 1TB etc.

About Memory Size

The byte is a unit of digital information that most commonly consists of eight bits.

1 Nibble = 4 bits 1Byte = 8 bits

1 Kilobyte (KB) = 1024 Bytes 1 Megabyte (MB) = 1024 KB

1 Gigabyte (GB) = 1024 MB 1 Terabyte (TB) = 1024 GB

1 Petabyte (PB) = 1024 TB 1 Exabyte (EB) = 1024 PB

1 Zettabyte = 1024 EB

CD-ROM

CD-ROM Drive

Magneto-Optical Disk

Cartridge Tape:

Memory Stick

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EXERCISES

Long Question :

1. Briefly explain the components of a system unit.

2. Differentiate between the characteristics of Primary and secondary storage

system of a computer.

Short Question:

1. Expand the following abbreviations used in computer terminology.

CD, DVD, SMPS, RAM, ROM, MB, GB

Fill in the blanks:

a. _________ is a read & write memory.

b. Primary memory is called __________ memory.

c. One byte equal to _________ bits.

d. One bit equal to _________. e. __________ is an example of secondary storage memory.

f. __________ is an example of primary storage memory.

g. State True or False. The microprocessor consists of ALU Unit, Control Unit, and Memory unit.

h. __________ is a unit of digital information that most commonly consists of

eight bits. (Ans. Byte)

i. Speed of a computer system is measured in terms of _________. ( Ans. MHz)