A
PC motherboard is the main
circuit board within a typical
desktop computer,
laptop or
server. Its main functions are as follows: • To serve as a central backbone to which all other modular parts such as
CPU,
RAM, and
hard drives can be attached as required to create a computer • To be interchangeable (in most cases) with different components (in particular CPU and
expansion cards) for the purposes of customization and upgrading • To distribute
power to other circuit boards • To electronically co-ordinate and interface the operation of the components As new generations of components have been developed, the standards of motherboards have changed too. For example, the introduction of
AGP and, more recently,
PCI Express have influenced motherboard design. However, the standardized size and layout of motherboards have changed much more slowly and are controlled by their own standards. The list of components required on a motherboard changes far more slowly than the components themselves. For example,
north bridge microchips have changed many times since their introduction with many manufacturers bringing out their own versions, but in terms of form factor standards, provisions for north bridges have remained fairly static for many years. Although it is a slower process, form factors do evolve regularly in response to changing demands. IBM's long-standing standard,
AT (Advanced Technology), was superseded in 1995 by the current industry standard
ATX (Advanced Technology Extended), which still governs the size and design of the motherboard in most modern PCs. The latest update to the ATX standard was released in 2007. A divergent standard by
chipset manufacturer
VIA called
EPIA (also known as ITX, and not to be confused with EPIC) is based upon smaller form factors and its own standards. Differences between form factors are most apparent in terms of their intended market sector, and involve variations in size, design compromises and typical features. Most modern computers have very similar requirements, so form factor differences tend to be based upon subsets and supersets of these. For example, a desktop computer may require more sockets for maximum flexibility and many optional connectors and other features on board, whereas a computer to be used in a
multimedia system may need to be optimized for heat and size, with additional plug-in cards being less common. The smallest motherboards may sacrifice CPU flexibility in favor of a fixed manufacturer's choice. The E-ATX form factor is not standardized and may vary according to the motherboard manufacturer. == Comparisons ==