The document discusses computer form factors and cases. It states that form factors specify physical dimensions to ensure interchangeability and proper fit. Cases contain most computer components and come in various sizes depending on the motherboard form factor, such as towers, desktops, and pizza boxes. Cases house components like the power supply, drives, and motherboard according to standard layouts defined by form factors.

1. Computer Form Factor
Computer Form Factor


In computing, a form factor specifies the physical
dimensions of major system components.
Specifically, in the IBM PC compatible industry,
standard form factors ensure that parts are
interchangeable across competing vendors and
generations of technology, while in enterprise
computing, form factors ensure that server modules
fit into existing Rackmount systems.
1 of 16

2. Computer Form Factor
Computer Form Factor
2 of 16

3. Computer Form Factor
Computer Form Factor


Traditionally, the most significant specification is
the motherboard, which generally dictates the
overall size of the case.
Small form factors have been developed and
implemented, but further reduction in overall size is
hampered by current power supply technology.
3 of 16

4. Computer Form Factor
Computer Form Factor
4 of 16

5. Computer Form Factor
Computer Case

A computer case (also known as a computer
chassis, cabinet, box, tower, enclosure, housing,
system unit or simply case) is the enclosure that
contains most of the components of a computer
(usually excluding the display, keyboard and
mouse).
5 of 16

6. Computer Form Factor
Computer Case



A computer case is sometimes incorrectly
referred to as a CPU.
Cases are usually constructed from steel or
Aluminium.
Plastic and wood are sometimes used.
6 of 16

7. Computer Form Factor
Computer Case: Sizes




Cases can come in many different sizes.
The size and shape of a computer case is usually
determined by the form factor of the motherboard,
since it is the largest component of most computers.
Personal computer form factors specify only the
internal dimensions and layout of the case.
Form factors for rack-mounted and blade servers
may include precise external dimensions as well,
since these cases must themselves fit in specific
enclosures.
7 of 16

8. Computer Form Factor
Rack Mounted Systems
8 of 16

9. Computer Form Factor
Blade Servers
9 of 16

10. Computer Form Factor
Computer Case: Sizes




Case designed for an ATX motherboard and power
supply may take on several external forms:
Vertical Tower (Designed to sit on the floor, height
> width)
Flat Desktop (height < width)
Pizza Box (height ≤ 2 inches, designed to sit on the
desk under the computer's monitor).
10 of 16

11. Computer Form Factor
Computer Case: Sizes
11 of 16

12. Computer Form Factor
Computer Case: Sizes



Tower cases come in mini-tower, mid-tower, and
big-tower/full-tower sizes.
Full tower cases are typically 22 inches or more in
height and intended to stand on the floor.
They have six to ten drive bays.
12 of 16

13. Computer Form Factor
Computer Case: Sizes


Midtower cases are smaller, about 18" high with
two to four external bays.
Minitower case will typically have only one or two
external bays and stand from 14" to 16" tall.
13 of 16

14. Computer Form Factor
Computer Case: Layout


Computer cases usually include sheet metal
enclosures for a power supply unit and drive bays,
as well as a rear panel that can accommodate
peripheral connectors protruding from the
motherboard and expansion slots.
Most cases also have a power button or
switch, a reset button, and LEDs to
indicate power status as well as
hard drive and network activity.
14 of 16

15. Computer Form Factor
Computer Case: Layout


Some cases include built-in I/O ports (such as USB
and headphone ports) on the front of the case.
Such a case will also include the wires needed to
connect these ports, switches and indicators to the
motherboard.
15 of 16

16. Computer Form Factor
Computer Case

Major Component Locations:
• The motherboard is usually screwed to the case along its
largest face, which could be the bottom or the side of the
case depending on the form factor and orientation.
• Form factors such as ATX provide a back panel with cutout holes to expose I/O ports provided by integrated
peripherals, as well as expansion slots which may
optionally expose additional ports provided by expansion
cards.
• The power supply unit is often housed at the top rear of
the case; it is usually attached with four screws to support
its weight.
16 of 16

17. Computer Form Factor
Computer Case

Major Component Locations:
• Most cases include drive bays on the front of the case; a
typical ATX case includes both 5.25" and 3.5" bays
• Buttons and LEDs are typically located on the front of
the case; some cases include additional I/O ports,
temperature and/or processor speed monitors in the
same area.
• Vents are often found on the front, back, and sometimes
on the side of the case to allow cooling fans to be
mounted via surrounding threaded screw holes.
17 of 16

18. Computer Form Factor
Computer Case

Internal access
• Tower cases have single side panel which may be
removed in order to access the internal components.
• Computer cases required screws to hold components and
panels in place (i.e. motherboard, PSU, drives, and
expansion cards).
• There is a trend toward "screwless" cases,
in which components are held together with
snap-in plastic rails, thumbscrews, and
other methods that do not require tools; this
facilitates quick assembly and modification
of computer hardware.
18 of 16

19. Computer Form Factor
Computer Case

Intrusion detection
• Some computer cases include a biased switch (pushbutton) which connects to the motherboard. When the
case is opened, the switch position changes and the
system records this change. The system's firmware or
BIOS may be configured to report this event the next time
it is powered on.
• This physical intrusion detection system may help
computer owners detect tampering with their computer.
19 of 16