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1. Computer Systems II
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2. Logical Block Diagram

3. System Unit
• System unit is created by inter-connecting lots
of parts.
• All of the components of a computer system
require power to perform.
• And also the system unit components needs
protection from out-side entities. (dust,
humidity, insects…..)

5. System unit cont……
• Therefore to provide,
– Power
– Protection
– Outer Appearance
Components of the system unit well organized
in side a ‘Protected Chassis’.

6. Chassis
• The chassis consist of space for,
– Motherboard
– Power supply
– Input/output connectors
– Expansion cards
– Expansion bays
– Switches and wires
– Indicator Light Emitting
Diodes (LEDs)

7. Chassis Types
• According to the outer appearance and the
device organization inside, chassis are differs.
• Mainly there are two types of Chassis using.
– Tower Chassis
– Flat-bed Chassis

8. Tower Chassis
• The system unit components are screwed on to the
right side panel of the chassis.
• The outer appearance looks like a ‘Tower’.
• Input/output connectors attached from the rear.
• More popular type in these days.
• There are some sub-types of Tower Chassis as well.

9. Tower Chassis Types
Mini-Tower
Mid-TowerFull-Tower

10. Flatbed Chassis
• The older version of chassis types.
• Very rarely used in these days.
• Branded computers still manufacturing these
types of chassis for office environments.
• Flatbeds are more compact and saves occupying
space.
• There are two types of Flatbed chassis.
– Desktop
– Slim Desktop

11. Desktop
Slim-Desktop

12. Power Supply
• Is the component that supplies power to a computer.
• More specifically, a power supply is typically designed to
convert 100-120 V (North America and Japan) or 220-
240 V (Europe, Africa, Asia and Australia)
• Provides 5V output by using 250Watt +
• Mainly Two types of Power Supplies are there,
» AT
» ATX

13. AT-Advanced Technology
• Older version of Power supplies.
• Power switch is not soft-switch one.
• Computer is connected directly to the power supply
ATX-Advanced Technology
Extended
• New version of Power supplies.
• Power switch is soft-switch one.
• Computer is connected to the power supply through
the motherboard.

14. Power supply connectors
• Power supply have many connectors to provide
power to the system components.
– Mini plug-provides power to the floppy drive
– Molex power connector-provides power to hard drives,
CD/DVD drives
– Motherboard power connector-provide power to the
motherboard
– 12v ATX power connector-this is required to provide
additional power to the Pentium4 processor. This is
plugged in to the motherboard.
– SATA (Serial Advanced Technology Attachment) power
connector-provides power to the SATA devices)

18. Drive bays
• Drive bays are a part of the chassis which is
used to attach drives such as the,
– Hard disk
– CD/DVD Drives
– Floppy drives.

19. Buttons and Indicators
• The power button and reset buttons are
located on the front panel of the chassis.
• With two LEDs for indicating the,
– HDD usage (Red)
– Power (Green)
Power
Reset

20. Components of the System Unit

21. Thank You !
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