The Motherboard
I would say that one of the most important components of a computer systems is the motherboard (otherwise known as the Main Board).

Since the first PCs hit the market, computer makers have followed the practice of placing most of the components of a system on one board.

The motherboard or system board as it's sometimes called, is a printed circuit board containing millions of micro circuits. The motherboard holds all of the chips required to make your computer work. Microchip s such as the microprocessor or Central Processing Unit (CPU) and supporting chips are found on this board.

The motherboard is the board that contains the logic circuits that tie all parts of your PC together. It provides the connectors for the CPU, the memory, BIOS, CMOS, Video devices, sound devices, storage devices, chip sets, etc. in order to form an integrated set of components.

Some of the key components found on a motherboard include:

  • The CPU (microprocessor
  • Microchips that provide support for the CPU.
  • Random Access Memory (RAM) chips.
  • The system Bus
  • A Keyboard controller and connector.
  • A mouse connector.
  • Power connectors.
  • Serial and parallel communications ports.
Some of the most recent boards also contain:
  • Intergrated IDE disk controller circuits.
  • USB Bus controller circuits.
  • Built in video controller/adapters.
  • Built in sound card circuits.
The motherboard also contains other components such as BIOS chips, the CPU clock, cache chips, bus, etc. To see every detail, you will need to get a "User's Manual" for the specific motherboard you have, and to locate all components on the board.

It is the system board components that determine the capability and speed of a computer. Several factors determine the overall performance of a system.

  • Speed - The processor clock speed, size of the internal and external data bus, and the processors design all determine the systems overall speed.

  • Configuration - The way the individual parts of the board are layered out and connected.

  • Memory - How much memory is on the board. What type of memory is being used.

  • Bus Type - Does the system support ISA, or PCI buses. The actual speed of the bus makes a difference.
There are two different types of motherboards used in computers today: the AT and ATX. Each one uses different design techniques depending on the CPU chip and bus type and size used.

Motherboards sizes are as follows:

  • Standard AT = 12" w x 13.8" long
  • Baby AT = 8.57" w x 13.04" long
  • LPX = 9.0" w x 13.0 long
  • ATX = 9.6" w x 12.00 long

Sizes are important if you are replacing an existing motherboard!

The ATX is the Intel specification released in July 1995. It has become the defacto industry standard for motherboards.

There are two basic types of chip connectors found on modern motherboards.

  • Dual In-line Package (DIP) DIP pins usually have two rows of 20 pins arranged as one row on each of two sides of the chip. This form was in heavy use in the early 1980s.

  • Pin Grid Array (PGA) - PGA pins use four rows of pins that surround the bottom of each chip.

Each of the components on a motherboard serve specific functions:

  1. BUS- The bus is actually a set of circuits that run throughout the board and connect all the expansion slots, memory, and CPU, etc. together.

  2. Expansion Slots - Used for connecting other devices/controller cards to the motherboard bus.

  3. Memory Slots - provides receptacles for adding additional memory chips (SIMMs, DIMMs, or other types of memory).

  4. ZIF Socket -The processor slot on modern boards is a grid of tiny holes in which the CPU is inserted. Older model boards required a considerable amount of force to install or remove the CPU chip. The Zero Insertion Force (ZIF) socket required a minimal force to insert and remove the chip. The ZIF socket has a lever at the side of the socket that allows quick removal of the CPU Chip.

  5. BIOS Chips - The method used in DOS to communicate with any device on the system such as disks, keyboard, monitor, etc. Directs only system hardware, not network hardware.

  6. USB Port - some newer machines will have a port for the Universal Serial Bus (USB) connection. The USB port will support up to 127 devices and runs at a speed of about 1.544MB.

  7. Chip Set The "Chipset" is the set of intergrated circuits that control most of the activities that take place on the motherboard. They also interface with most of the circuits of the motherboard.

In some cases a system will not have a full motherboard. The chips normally found on a motherboard are on a separate adapter card which plugs into a connector. In this case the plug in board is called a backplane or planar board and contains the expansion slots.