Module 3

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Module 3

• Assembling a Computer

Version 3.1
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Before beginning any assembly process, it is a
good idea to review safety procedures.

• Keep the work area free of clutter and keep it
  clean.
• Keep food and drinks out of the work area.
• A computer monitor may store up to 25,000 volts,
  so avoid opening one unless trained to do so.
• Remove all jewelry and watches.
• Make sure the power is off and the power plug has
  been removed when working inside the computer.
• Never look into a laser beam. Lasers are found in
  computer related equipment.
• Make sure that a fire extinguisher and first aid
  kit is available.
• Cover sharp edges with tape when working inside
  the computer case.

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Basic Safety Procedures

• Use an antistatic mat and grounding wrist strap.
• Use antistatic bags to store and move computer
  components.
• Do not remove or install components while the
  computer is on.
• Ground often to prevent static charges from
  building up by touching a piece of bare metal on
  the chassis or power supply.
• Work on a bare floor because carpets can build up
  static charges.
• Hold cards by the edges to avoid touching chips
  or the edge connectors on the expansion cards.

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Basic Safety Procedures

• Do not touch chips or expansion boards with a
  magnetized screwdriver.
• Turn off the computer before moving it. This is
  to protect the hard drive, which is always
  spinning when the computer is turned on.
• Do not place a circuit board of any kind onto a
  conductive surface.
• Do not use a pencil or metal tipped instrument to
  change DIP switches or to touch components. The
  graphite in the pencil is conductive and could
  easily cause damage.
• Do not allow anyone who is not properly grounded
  to touch or hand off computer components. This is
  true even when working with a lab partner. When
  passing components, always touch hands first to
  neutralize any charges.

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ESD Precautions

• Electrostatic discharge (ESD) is more commonly
  referred to as static electricity.
• ESD is probably the greatest enemy when a user
  unwraps newly purchased computer parts and
  components while preparing to assemble the
  computer.
• The best way to protect against ESD is to use an
  anti-static mat, a grounding wrist strap, and
  anti-static bags.

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ESD Precautions

• Always review the ESD precautions before
  beginning the assembly process.
• Keep all computer parts in anti-static bags.
• Keep the humidity between 20 - 30 percent.
• Use grounded mats on workbenches.
• Use grounded floor mats in work areas.
• Use wrist straps when working on computer parts,
  except when working on monitors or power
  supplies.
• Periodically touch unpainted grounded metal parts
  of the computer to lower the static energy of the
  body.

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Computer Cases

• There are three basic types of computer cases
• Desktop
• Tower
• Mini-tower
• Mid-tower
• Full tower
• Portable
• Whether buying a tower or desktop, it is
  recommended that it conforms to the ATX standard
  and has at least a 250-watt power supply (300
  watts is ideal.)
• The desktop case is considered the most difficult
  to upgrade.

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Desktop Computers

• The desktop design is one of the more familiar
  case styles. Desktop units are designed to sit
  horizontally on the desktop.
• The two important considerations in choosing a
  desktop case style for a computer are
• Available desktop space
• Form factor
• The newest form factor, and the one most often
  encountered, is the ATX.

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Tower Computers

• Tower cases are usually designed to sit
  vertically on the floor beneath a desk.
• Tower cases come in three sizes
• Mini towers
• Mid towers
• Full-size towers

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Power Supplies

• The power supply is one of the most important
  parts that needs to be understood. The power
  supply unit provides electrical power for every
  component inside the system unit.
• The power supply plays the critical role of
  converting commercial electrical power (AC), into
  DC required by the components of the computer.
• There are two basic types of power supplies
• AT power supplies Designed to support
  AT-compatible motherboards. 
• ATX power supplies Designed according to newer
  ATX design specifications to support the ATX
  motherboard.

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Power Supplies

• There are two major distinctions between the
  legacy AT and the new ATX power supplies.
• The AT power supply has two 6-pin (12 pins)
  motherboard power connectors (P8/P9)
• The ATX power supplies use a single 20-pin power
  connector (P1).
• In the ATX-compatible power supply, the cooling
  fan pulls air through the case from the front and
  exhausts it out the rear of the power supply
  unit.
• The AT design pulls air in through the rear of
  the power supply unit and blows it directly on
  the AT motherboard.

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Power Supplies

• The power supply produces four (five in the ATX)
  different levels of well-regulated DC voltage for
  use by the system components.
• These are 5V, -5V, 12V, and -12V.
• In ATX power supplies, the 3.3V level is also
  produced and is used by the second-generation
  Intel Pentium processors.

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Power Supplies
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Motherboard Location Map

• A motherboard location map shows where the major
  components and hardware is located on the
  motherboard. A motherboard map can be found in
  the documentation that comes with the motherboard.

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Configuring the Motherboard

• Configuring the motherboard typically means the
  following
• Installing the CPU
• Installing the heat sink and fan
• Installing RAM
• Connecting the power supply cables to the
  motherboard power connectors and connecting
  miscellaneous connectors to the correct switches
  and status lights on the front case panel.
• Setting the system BIOS

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Configuring the Connectors

• For the disk controllers, always remember that a
  colored stripe on the data cable is pin-1.
• Most modern connectors are "keyed" by a missing
  pin or a blocked connector, so they cannot be
  fitted the wrong way.
• Usually, the colored wire(s) in a power cable are
  positive and the white or black wire(s) are
  ground or negative.

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CPU Interfaces

• There are two main types of CPU interfaces.
• Socket type (e.g., socket 7) - Socket 7 has been
  the standard interface, although the newer
  systems are now using different sockets. It is
  the only interface used by at least one
  generation of Intel Pentium processors (Pentium
  I) as well as AMD and Cyrix chips.
• Slot type (e.g., slot 1.) - Slot type interfaces
  use a slot similar to expansion cards. Slot 1 is
  the Single Edge Contact (SEC) interface used only
  by the Intel Pentium II processor family.

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RAM

• The two types of memory modules used on most PCs
  are
• Dual Inline Memory Module (DIMM)
• Single Inline Memory Module (SIMM)

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RAM

• Dual Inline Memory Module (DIMM)
• 168-pin
• DIMM cards are inserted straight into the slots
• When DIMM sizes are mixed on the motherboard, it
  is important to remember to put the DIMM with the
  largest memory size in the first bank.

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RAM

• Single Inline Memory Module (SIMM)
• 72-pin
• SIMM cards are inserted at an angle of about 45
  degrees
• Each bank of memory for a SIMM has two sockets.
  You must fill the first bank before moving onto
  the next. Additionally, each bank must be filled
  with RAM modules that have the same access time
  and size.

NOTE A bank is a group of memory slot used to
install RAM
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RAM

• Rambus Inline Memory Module (RIMM)
• 184 pins
• RIMM modules use only the direct Rambus memory
  chips (RDRAM)
• RDRAM is characterized by its high bus speed.
• RIMMs require that if you do not fill all RIMM
  slots with RDRAM memory, you must keep the empty
  slots filled with termination boards

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Connecting the Power Supply

• The power supply converts the alternation current
  (AC) line from your home to the direct current
  (DC) needed by the personal computer.
• This process will vary depending on the type of
  motherboard that is being installed (AT or ATX).
• Sometimes it is helpful to delay attaching the
  power connector to the board until all the
  components have been installed that need to go
  on the motherboard.
• This allows for more working space inside the
  case.

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Connecting the Power Supply

• WARNING Do not open the power supply it contains
  a capacitors which can hold Electricity (WHICH
  CAN KILL) even if the computer is power off for a
  week, if not longer. If you do open it WHICH IS
  NOT RECOMMENDED, take all precautions and ensure
  you work with one arm behind your back to direct
  the electricity away from the heart. Also ensure
  that you have no jewelry on (such as a watch or
  rings). However again THIS IS NOT RECOMMENDED and
  still cannot protect you 100 and is still
  potentially dangerous.

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AT Power Supply

• AT power supplies are considered legacy
• AT motherboards have a 12 pin connector and the
  AT power supply has two 6 pin connectors (P8 and
  P9).
• Plug the P8 and P9 wire lead connectors in the
  12-pin power connector.
• Make sure the black wires are in the middle,
  right next to each other or the motherboard could
  be damaged.

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ATX Power Supply

• ATX is currently the most common type of power
  supply.
• ATX motherboards have a single 20 pin connector
  (P1).
• The connector is keyed for easy installation.

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Connecting Floppy Drives

• The floppy drive exchanges data with the
  motherboard devices, including the
  microprocessor, via a 34-pin flat ribbon (data)
  cable
• Usually, a red stripe on the edge of the cable
  identifies pin-1. Lining the red-stripe edge with
  pin-1 of the drive connector or drive controller
  interface assures a correct alignment.
• If the cable is incorrectly oriented it becomes
  immediately apparent on power up by the fact that
  the floppy drive LED light comes on immediately
  and stays on.

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Connecting Floppy Drives

• Current system BIOS versions can support up to
  two floppy drives on one controller via a daisy
  chain cable arrangement. Cable pin-outs 10
  through 16 are cross-wired between the middle
  drive connector and end drive connector,
  producing a twist that reverses the Drive Select
  (DS) configuration of the drive plugged into the
  end connector of the ribbon cable. This feature,
  called cable select, automatically configures the
  drive on the middle connector as Drive B and the
  drive on the end connector as Drive A.

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Installing a Hard Drive or CD-ROM

• Attaching the hard drive and CD-ROM are basically
  similar.
• First, the jumper settings should be properly
  set.
• The designation of a hard drive or CD-ROM drive
  as either master or slave is generally determined
  by the jumper configuration, not by the order in
  which the drive is daisy-chained to the other
  drive.
• The hard drive that is used to boot the computer
  should be set as the primary master
• The only exception is if the drive is jumpered
  (set to) "cable select" and both the system and
  ribbon cable support cable select.

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Connecting a Hard Drive or CD-ROM

• Hard drives and CD-ROM drives communicate with
  the rest of the system using ribbon cables.
• Ribbon cables are widely used to connect
  peripherals such as floppy drives and hard drives
  internally.
• IDE cable ribbon cables used for hard drives and
  CD-ROM drives typically have 40 pins and can
  connect two devices to each cable.

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Power On Self Test

• Whenever a computer starts up, a series of tests
  are automatically performed to check the primary
  components in the system, such as the CPU, ROM,
  memory, and motherboard support circuitry.
• The routine that carries out this function is
  referred to as the POST.
• POST is a hardware diagnostics routine that is
  built into the system BIOS.
• The basic function of the POST routine is to make
  sure that all the hardware the system needs for
  startup is there and that everything is
  functioning properly before the boot process
  begins.

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Power On Self Test

• POST also provides some basic troubleshooting to
  determine what devices have failed or have
  problems initializing during this pre-startup
  hardware check.
• The POST routine provides error or warning
  messages whenever it encounters a faulty
  component.
• Post error codes take the form of a series of
  beeps that identify a faulty hardware component.

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Power On Self Test

• If the Post advances up to the point where video
  can be displayed, the error codes are displayed
  on the monitor.