The document discusses the components and organization of a computer system unit. It describes how the system unit houses and protects components like the motherboard, power supply, expansion cards, and drives. There are two main types of chassis - tower and flatbed. A tower chassis resembles a tower with components screwed onto the right side panel and inputs/outputs on the rear. A flatbed chassis is more compact and saves space. The power supply converts mains power and provides different voltages to components via various connectors. Drive bays hold storage drives and buttons and LEDs on the front panel control and indicate power and HDD usage.

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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