System Unit

System Unit
Major Components and its function

Major Components
• Motherboard
• Processor
• Physical Memory (RAM)
• Drives
• Data Cables
• PSU (Power Supply Unit)
• Cooling Devices
• Expansion Cards (Add on cards)
• System Case
Motherboard
• The motherboard is the main circuit board in the computer. It
is the biggest circuit board found inside the computer.
• Its main function is to allow the Central Processing Unit (CPU),
the "brain" of the computer, to communicate with other
components.
• A motherboard is a thin flat piece of circuit board, usually of
green or gold color.
• The motherboard has sockets to connect various components
like Keyboard, Mouse, Disk drives, PC cards etc. to the
computer.
• Copper circuit paths called traces that resemble a complicated
roadmap carry signals and voltages across the motherboard.
Motherboard Form Factor (size)
E-ATX - 12 × 13 in (305 × 330 mm) 1996

STANDARD ATX - 12 × 9.6 in (305 × 244 mm) 1995
MICRO-ATX - 9.6 × 9.6 in (244 × 244 mm), but some micro-ATX boards can be as
small as 6.75 × 6.75 in (171.45 × 171.45 mm) 1997
ITX - 17 × 17 cm (6.7 × 6.7 in) 2001
PICO ITX - 10 × 7.2 cm (3.9 × 2.8 in) 2007
Processor (CPU)
• A programmable
logic device that
performs all the
instruction, logic,
and mathematical
processing in a
computer.
CPU Manufacturers
• Intel
• AMD (Advance Micro Devices)

CPU Components
1. The Control Unit:
– It receives messages from INPUT devices like,
Mouse and keyboard.
– It then decodes the instruction from input devices
and sends them to the ALU(Arithmetic Logic Unit)
to be acted upon.
– Finally it sends the processed information into
storage or to OUTPUT devices (like your screen or
printer).
CPU Components
2. The Arithmetic Logic Unit (ALU):
– calculations (adding, subtracting, multiplying and

dividing).
– logic functions (comparing numbers, letters or

special characters and then making decisions
based on the results.)
Memory
RAM (Random Access
Memory)
is a temporary memory.
The computer uses it to
store data and
instructions while it is
working. When the
computer is switched off
this information is lost.
Types of RAM
• SD (Synchronous Dynamic)
• DDR (Double Data Rate)
Pin Counts:
SD = 168 pins
DDR1 = 184 pins
DDR2 = 240 pins
DDR3 = 240 pins
Memory
ROM (Read Only
Memory)
is a permanent store
of instructions which
cannot be erased or
changed and is not lost
when the power is
switched off.
Drives
HDD (Hard Disk Drive)
A hard drive is a
storage device located
inside the computer. It is
called hard drive
because the disks are
located inside the box.
Drives
OPTICAL DRIVE
Allow the system to access

(read/write) the CD/DVD disk
Types of Drives interface
Drives Interface
Data Cables
• Used to connect drives to the motherboard to
have an access of the information (files) from
the storage devices.
Types of Data Cables:
• PATA (Parallel Advanced Technology Attachment) or
IDE (Integrated Drive Electronics)
• SATA (Serial Advanced Technology Attachment)
Data Cables
IDE/PATA SATA
PSU (Power Supply Unit)
• The power supply
provides the necessary
electrical power to make
the computer operate.
• The power supply takes
standard 230-volt AC
power and converts it
into 12 volts, 5 volts and
sometimes 3.3-volt DC
power.
Power Supply Connectors
Cooling Devices
• A device that helps the computer system to
reduce the heat.
Classes:
• Heat sink
• Fan
• Coolers (Heat sink + Fan)
• Heat Pipe
Cooling Devices
Heat Sink Coolers Heat Pipe

Expansion Cards (Add on cards)
• The purpose of these Common cards
cards is to connect an • Video/Graphics card
external device to the • Sound card
computer and allow • LAN card
the interaction from a • Modem card
user to the computer • USB card
and also the device to
the computer.
Video card
• is an expansion card
which generates a
feed of output images
to a display (such as a
computer monitor).
Sound card
• is an
internal computer ex
pansion card that
facilitates the input
and output of audio
signals to and from a
computer under
control of computer
programs.
LAN card
• is a computer
hardware component
that connects
a computer to a
computer network.
Modem card
• is a device that
modulates an
analog carrier signal
to encode
digital information
and demodulates
the signal to decode
the transmitted
information.
Computer Case
• The system case, sometimes called the chassis
or enclosure, is a metal and plastic box that
houses the main components of the computer.

System Unit

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System Unit

Major Components and its function

E-ATX - 12 × 13 in (305 × 330 mm) 1996

• AMD (Advance Micro Devices)

– calculations (adding, subtracting, multiplying and

– logic functions (comparing numbers, letters or

Allow the system to access

Heat Sink Coolers Heat Pipe

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