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computer maintenance and

technical support(ITec3031)
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Chapter 2
Computer cases and the Motherboard
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By Abinet B.
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 Computer cases

 System units may be packaged in a number of standard case designs.

 Each design offers characteristics that adapt the system for different
environments. The key characteristics for case design include
mounting methods for components, ventilation characteristics, drive
capacity, and footprint (desk space they take up).
 is the metal and plastic box that houses the main components of the
Computer
 The computer case serves critical functions much as skin does for the
human body.

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 Continued..
 System cases protect the computer chassis, hard drive,
motherboard, and other internal components of the
computer.
 There are many factors that must be considered when
choosing a case:
 The size of the motherboard
 The number of external or internal drive locations
called bays
 Available space
 NOTE: You should select a case that matches the
physical dimensions of the power supply and
motherboard.

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 Types of Computer Cases
Tower Case (Full(5+), Midi(3-4) and
Mini(1-2))
These cases usually support up to
multiple drive bays, and as a result, are
the most expensive computer cases in
the market.
Tower cases are differentiated by the
number of drive bays that they support.
Desktop Case-case in which the monitor
sits on top of the case has the fewest
alternative available on the market.
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 Continued..
Portable Case-is usually the lightest and the
most portable in the market. Commonly use by
Notebooks, Laptops, Tablet PC Case…etc
All-In-One-Case-This type of case is very
popular with Apple computers, it is slim and cool
looking.
 Inside the System Unit
 The components inside the system unit can be
divided into four distinct subunits: a switching
power supply, the disk drives, the system
board, and the options adapter cards

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 1. power-supply
 It convert alternating-current (AC) power from the wall
socket into direct-current (DC) power lower voltage
 The size and shape of the computer case is usually
determined by the motherboard and other internal
components.
 An uninterruptible power supply (UPS) can protect a
computer from problems caused by changes in power
-You should select a case that matches the physical
dimensions of the power supply and motherboard.
The number and types of disk drives installed in a
system varies according to the intended use of the system.

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 Continued..
There are two types of cables inside the case:
data cables, which connect devices to one
another, and power cables or power cords,
which supply power
 2. disk drive =floppy disk drive (FDD) unit, a
single Hard Disk Drive (HDD) unit, and a single
CD-ROM drive are typically installed to handle
the system’s mass-storage requirements.
3. system board -is the main circuit board of
the PC. It contains all the basic, core components
of the computer.
 System boards also are referred to as
motherboards, main boards, or planar boards
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 Continued..
4. adapter cards permit a wide array of
peripheral equipment to be added to the basic PC
system.
expansion cards or simply cards, are installed in
long narrow expansion slots on the motherboard
The most frequently installed adapter cards in
PC systems are video adapter cards
Peripheral devices, such as printers and
modems, normally connect to adapter cards
through expansion slot openings in the rear of
the system unit
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 System cover removal and replacement
Standard Method:
 Undo 4-6 screws or one on the back of the
case
 Slide the cover back about an inch
 Lift the cover off
No Manual? Follow these steps:
 Carefully inspect the case
 Don't force anything; it may break
 Check for separation between sides and top
 Remove sides and top separately if necessary
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 System cover removal and replacement

Handling the Case:

After removal, place the case in a safe location
Avoid knocking, kicking, or stepping on it
Prevent bending or damage
Replacement:
Bring the new case
Position it correctly
Slide it into place

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Removing External I/O Systems
 Unplug all power cords from the commercial outlet.
 Remove all peripherals from the system unit.
 Disconnect the mouse, keyboard, and monitor signal
cable (VGA cable) from the rear of the unit
Removing the System Unit’s Outer Cover
 Unplug the AC power cord from the system unit.
 Determine which type of case you are working on
 If the case is a desktop model, does the cover slide off
the chassis in a forward direction, bringing the front
panel with it, or does it raise off of the chassis from the
rear?
 If the retaining screws go through the back panel
without passing through the lip, the outer cover will
slide forward after the retaining screws have been
removed.
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 System board
 The largest and most
important circuit board in
the computer is the
motherboard, also called the
main board, the system
board, or the techie jargon
term, the moboard.
 The major components of
interest on a PC system board
are the microprocessor, the
system’s primary memory
sections (read-only [ROM],
random-access [RAM], and
cache memory), expansion slot
connectors, and microprocessor
support ICs that coordinate the
operation of the system.
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 Major Components
Microprocessors-
Is the Major component of the system board.
Acts as the "brains" of the computer system
CPU installed on the motherboard
All devices connected to the motherboard:
 Directly (via ports or cables)
 Indirectly (via expansion cards)
 Devices not directly installed on the motherboard
Referred to as peripheral devices

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 Continued..
For instance Intel have many versions like Intel core
i3, i5, i7 the latest versions
 Primary Memory (RAM)-All computers need a
place to temporarily store information while other
pieces of information are processed.
which holds data and instructions as they are
processed
Primary storage is much faster to access than
permanent storage
RAM chips are embedded on a small board that
plugs into the motherboard
These small RAM boards are called memory
modules, and the most common type of module is
the DIMM (dual inline memory module)
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 Continued..
-primary memory (made up of semiconductor RAM and
ROM chips), and
-mass-storage memory (usually involving floppy and hard
disk drives).
 Primary memory typically exists in two or three
forms on the system board:
 Read-only memory (ROM): - Contains the computer’s
permanent startup programs
 Random-access memory (RAM): - Quick enough to
operate directly with the microprocessor and can be
read from, and written to, as often as desired.
 Cache memory: - A fast RAM system specially
designed to hold information that the microprocessor
is likely to use.

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 Continued..
RAM is a volatile memory(information is stored in
RAM is lost when the computer is turned off). ROM, on
the other hand, is nonvolatile.
 Chipsets -As manufacturers improved
techniques for creating ICs, the number of
transistors on a chip grew and complex digital
circuits were fabricated together
- The chipset is responsible for the careful
timing and coordination of activities
- The processor could not do its job without
the assistance of the chipset
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 Continued..
 Chips to control basic devices such as hard disks,
floppy disks, serial/parallel ports etc.
 These basic digital devices still exist and occupy a
class of ICs referred to as small-scale integration
(SSI) devices
 Eventually, large-scale integration (LSI) and very
large-scale integration (VLSI) devices were
produced. LSI devices contain between 3,000 and
100,000 electronic components.
 VLSI devices exceed 100,000 elements.

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 Secondary Storage
 RAM installed on the motherboard is called
primary storage.
 Primary storage temporarily holds both data and
instructions as the CPU processes them.
 These data and instructions are also permanently
stored on devices, such as DVDs, CDs, hard drives,
and USB drives, in locations that are remote from
the CPU
 Data and instructions cannot be processed by the
CPU from this remote storage (called secondary
storage), but must first be copied into primary
storage (RAM) for processing
 When you turn off your computer, the
information in secondary storage remains intact
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Motherboard Components Used For Communication
 Traces on Motherboard:
 Fine lines on the top and bottom
surface
 Circuit paths enabling data,
instructions, and power flow
 Bus Definition:
 System of pathways for communication
Includes protocols and transmission
methods
 Data Bus:
 Lines of the bus used for data
 Facilitates data transmission between
components
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 Types of Form Factors:
 The term form factor is used to refer to the physical
size and shape of a device
 Also it describes the general locations of components
and parts.
 it also refers to their case style and power-supply
compatibility, as well as to their I/O connection
placement schemes
 AT Advance Technology (older model )
 ATX Advance Technology Extended (most popular type
of computer case use today)
 BTX Balance Technology Extended (newest form factor
known as the cooling case)
 SFF Small Form Factor
 ITX Type of case found on a lot of mini and micro
computers
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 System Board Form Factors
1. ATX Form Factor (Full ATX)
 the most common form factor for a motherboard
 It includes advanced control facilities, where the BIOS
program continually checks the CPU temperature and
voltages, the cooling fans, etc.
 If over heating occurs, the PC will shut down
automatically
 The board is approximately 30cm x 24cm
 Mini ATX-a slightly smaller variation of the full ATX size
that measures 28cm x 21cm. A case that supports an
ATX motherboard can also support mini-ATX
motherboard.
 Difference b/n ATX and mini-ATX is the number of buses
and possibly memory slots on the motherboard
The busses are the nerve system of system board. They
connect the CPU to all the other components
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 Continued..
 The system bus, which connects the CPU with RAM
 I/O busses, which connect the CPU with other
components.
 Micro ATX-is an even smaller version of the ATX
standard with a maximum size of 24cm x 24cm.
 System case that can hold an ATX motherboard can
also hold micro ATX motherboard.
 The terms mini-ATX and micro-ATX are often used
interchangeably.
 the ATX specification for the power-supply
connection calls for a single, 20-pin power cord
between the system board and the power-supply
unit

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Removing and replacing motherboard
 The removal procedure can be defined in five steps,
Removing a System Board
1. Remove all external I/O systems.
2. Remove the system unit’s outer cover.
3. Remove the option adapter cards.
4. Remove the cables from the system board.
5. Remove the system board
 To replace a system board, it is necessary to disconnect
several cables from the old system board and
reconnect them to the new system board

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 Troubleshooting System Board
Troubleshooting problems related to the
system board can be difficult to solve because of
the system board’s relative complexity
 begin by observing the symptoms produced by
boot up and operation.
 Observe the steps that lead to the failure and
determine under what conditions the system
failed. Were any unusual operations in
progress? Note any error messages or beep
codes.
 checking for loose connections on peripheral
equipment

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 Continued..
 Retry the system several times to observe the
symptoms clearly.
 Take time to document the problem—write it down.
 Refer to the User Manuals for the system board and
peripheral units to check for configuration problems
 Examine the CMOS(complementary metal-oxide
semiconductor) setup entries for configuration
problems
 If the diagnostics program indicates a number of
possible bad components, replace them one at a
time until you isolate the bad unit. Then insert any
possible good units back into the system and check
them.

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 System Board Symptoms
So much of the system’s operation is based
on the system board that it can have several
different types of symptoms.
The On/Off indicator lights are visible, the
display is visible on the monitor screen, but
there is no disk drive action and no boot up
The On/Off indicator lights are visible, the
hard drive spins up, but the system appears
dead and there is no boot up
The system locks up during normal
operation.
The system produces a beep code with 1, 2,
3, 5, 7, or 9beeps
The system will not hold date and time 26
 System Board Symptoms
An 8042 Gate A20 Error message displays—error
getting into protected mode.
An Invalid Switch Memory Failure message
displays.
A CMOS Battery Low message displays, indicating
failure of CMOS battery
A 201 error code displays, indicating a RAM
failure.
A parity check error message displays, indicating
a RAM error
 A CMOS Time & Date Not Set message displays—
system configuration and setup failure
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 Continued..
Typical symptoms associated with system board I/O
failures include the following:
Speaker doesn’t work during operation. The rest of the
system works, but no sounds are produced through the
speaker.
Keyboard does not function after being replaced with a
known good unit.
The system board normally marks the end of any of the
various troubleshooting
First, the system board supports most of the other
system components, either directly or indirectly.
Second, it is the system component that requires the
most effort to replace and test.
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