A Guide to PC Hardware Maintenance and Repair

1
Chapter 2 PC Basics
2
Objectives

• To get an overview of the basic components of the
  PC
• Receive an introduction to PC Busses
• Take a tour of the motherboard

3
Internal Components

• Motherboard
• CPU
• RAM
• Hard disk
• Motherboard ports
• Expansion cards
• Cables

4
The Motherboard

• Form Factor
• AT (obsolete)
• ATX
• LBX

5
Power Connectors

• AT consists of two connectors. Incorrect
  placement will kill the motherboard.
• ATX and others are keyed single connectors.

The AT power plugs in this image are reversed.
This will kill the motherboard!!
6
The Expansion Bus

• Consists of several expansion slots
• PCI
• PCI-X
• AGP
• Older boards will still have ISA slots

ISA Slots
PCI Slots
AGP Slot
7
Memory Sockets

• Modern boards have DIMM or Rambus DIMM
• Older boards may still have SIMM sockets

DIMM Sockets
SIMM Sockets
8
CPU Sockets

• CPU Sockets vary in physical configuration.
• They also vary in electrical specifications.

9
The Chipset

• Dictates practically every aspect of the computer
• CPU type and speed
• Memory type, speed and capacity
• Device support
• Consists of two or more chips

10
System BIOS

• Basic Input Output Services
• Contains startup routines for the system
• Provides the basic command set for system devices

11
Onboard Connectors
Floppy Disk Controller

• IDE ports
• Usually just two
• Some boards support IDE RAID and have four
• 40 pins
• Floppy Disk controller
• Just one
• 34 pins

IDE Ports
12
Backplane Connectors
Parallel Port
Mouse Connector
Keyboard Connector
USB Ports
Serial Ports
13
The VGA Connector

• 15-pin D-shell connector
• Its the only connector on the back of the PC
  with three rows of pins.

14
Sound Cards

• 2 to 4 1/8 mini-jacks
• Most have a 2-row 15-pin D-shell connector
• May be onboard or installed as a separate
  expansion card

15
Expansion Cards

• PCI
• The vast majority of cards youll see today
• ISA
• Considered obsolete, but there are still many
  installed
• AGP
• Only used for video

16
PCI Cards

• 22 pins per inch
• Notched edge card with notch 2.5 from front of
  connector

17
AGP Cards

• Only video cards are AGP
• Edge card is offset from back of computer by 2.5
• 1/8 notch is located about 1/3 of the way to the
  back of connector.

18
ISA Cards

• Rarely (if ever) seen on new computers
• Only operate at 8.33Mhz
• 10 pins per inch

19
Modems

• Typically have two RJ-11 (telephone) connectors
• May be onboard the motherboard or installed as a
  separate expansion card

20
Network Interface Cards

• Contains a single RJ-45 connector that resembles
  a telephone connector, but is larger.
• 8 connectors
• Very old NICs may have a 15-pin D-shell connector
  similar to the one on a sound card.

21
The Power Supply

• Larger silver box, usually toward the top of the
  enclosure
• Most have 115/220V switches installed

22
Drive Bays
Half-height

• Full height
• Rarely seen these days
• Half-height
• Typical 5.25 drive bay
• 1 height
• Used for floppy drives and zip drives

1 external
1 internal
23
The Backplane

• Location of external ports for all expansion
  cards installed.
• I/O ports for mouse, keyboard, serial and
  parallel, and USB ports as well.