How Motherboards Work

By: Tracy V. Wilson & Ryan Johnson

Form Factor

A modern motherboard.
A modern motherboard.
Photo courtesy Consumer Guide Products

A motherboard by itself is useless, but a computer has to have one to operate. The motherboard's main job is to hold the computer's microprocessor chip and let everything else connect to it. Everything that runs the computer or enhances its performance is either part of the motherboard or plugs into it via a slot or port.

The shape and layout of a motherboard is called the form factor. The form factor affects where individual components go and the shape of the computer's case. There are several specific form factors that most PC motherboards use so that they can all fit in standard cases. For a comparison of form factors, past and present, check out


The form factor is just one of the many standards that apply to motherboards. Some of the other standards include:

  • The socket for the microprocessor determines what kind of Central Processing Unit (CPU) the motherboard uses.
  • The chipset is part of the motherboard's logic system and is usually made of two parts -- the northbridge and the southbridge. These two "bridges" connect the CPU to other parts of the computer.
  • The Basic Input/Output System (BIOS) chip controls the most basic functions of the computer and performs a self-test every time you turn it on. Some systems feature dual BIOS, which provides a backup in case one fails or in case of error during updating.
  • The real time clock chip is a battery-operated chip that maintains basic settings and the system time.

The slots and ports found on a motherboard include:

A Socket 754 motherboard
A Socket 754 motherboard
Photo courtesy Consumer Guide Products

Some motherboards also incorporate newer technological advances:

  • Redundant Array of Independent Discs (RAID) controllers allow the computer to recognize multiple drives as one drive.
  • PCI Express is a newer protocol that acts more like a network than a bus. It can eliminate the need for other ports, including the AGP port.
  • Rather than relying on plug-in cards, some motherboards have on-boardsound, networking, video or other peripheral support.

Many people think of the CPU as one of the most important parts of a computer. We'll look at how it affects the rest of the computer in the next section.