Motherboard Basics

A recent Tech Tip covered the basics of selecting a computer case and made mention of the various sizes that correspond to motherboards of different form factors. A few people wrote in expressing interest in understanding more about the basics of motherboards, and that's exactly what this Tech Tip intends to address.

A motherboard, also known as a main board, is the primary circuit board inside of a computer, and is where the central processing unit (CPU), memory, expansion slots, drives, and other peripheral devices are connected. The circuitry on a motherboard facilitates the communication between all of the devices in the computer, making them as critical to a system's performance as items such as the CPU or memory.

The core circuitry of a motherboard is referred to as its chipset, and generally the manufacturer of the motherboard is not the manufacturer of the chipset. Intel does produce motherboards with their own chipsets, but buying a motherboard brand such as Gigabyte, Biostar, and ASUS means getting a board with either a VIA, Nvidia, SIS, or Intel brand chipset.

1. Form Factor

The different basic shapes and sizes of motherboards are categorized as form factors. There are several standard form factors available, but some of the more common ones found in desktop computers include:(http://www.formfactors.org/developer/specs/atx2_2.pdf), ATX (http://www.formfactors.org/developer/specs/matxspe1.2.pdf), Micro ATX (mATX) (http://www.formfactors.org/developer/specs/FlexATXaddn1_0.pdf) FlexATX (http://www.via.com.tw/en/initiatives/spearhead/mini-itx/) and Mini-ITX

The basic sizes of each are as follows:

* ATX: 12" x 9.6" (305mm x 244mm)

* Micro ATX: 9.6" x 9.6" (244mm x 244mm)

* FlexATX: 9.0" x 7.5" (229mm x 191mm)

* Mini ITX: 6.7" x 6.7" (170mm x 170mm)

ATX and mATX are by far the most popular motherboard sizes for desktop computers, and as seen in the list above, are also some of the largest. More real estate on a motherboard allows for greater expansion possibilities and extra features, which make the use of these boards more flexible. A Mini-ITX board may feature just one slot for memory and one slot for an expansion card, while a typical ATX board may feature 4 memory slots and six slots for expansion cards.

Each form factor has its own niche that it fits into, from workstations and gaming systems for larger boards to media centers and in-car computers for smaller boards. There is definitely overlap between the potential applications of each form factor, and other features and capabilities will also influence the targeted use.

2. CPU Socket

The major processor manufacturers, AMD and Intel, are constantly waging a battle to offer the fastest, most powerful processors available. Getting more speed and performance out of a relatively small chip generally requires a change to the physical dimensions as each new generation of processor is released. Therefore, motherboards need to evolve at the same pace in order to accept the new CPUs.

Back in the day, AMD and Intel processors shared a common CPU socket, but those days were short lived. AMD and Intel have since been traveling down their own, relatively parallel, paths of performance and speed increases, while using different designs. Selecting a motherboard for a modern AMD processor eliminates the use of any Intel processor, and vice versa.

AMD's current offering for desktop processors includes the Athlon 64, which is available in Socket 939 and Socket 754 formats. The number in the names represents the number of pins present on the backside of the CPU that connect to the motherboard's socket. The Socket 939 Athlon 64 therefore has a staggering array of nine hundred and thirty nine tiny pins to match up with the motherboard's socket. The Chaintech VNF4 Ultra is an example of a Socket 939 motherboard based on Nvidia's NForce4 Ultra chipset technology. In addition to these two sockets, many AMD processors, including Athlon XPs, Semprons, and Durons, share the Socket A format, also known as Socket 462 thanks to it having 462 pins for connecting to a motherboard.Socket adapters

Intel's latest offering for their Pentium 4 and Celeron processors, LGA 775, doesn't have pins at all and basically swaps the pins to the motherboard for the socket. Perhaps this design move puts the burden of bent pin warranty cl