ATX

ATX (Advanced Technology eXtended) is a motherboard form factor specification developed by Intel in 1995 to improve on previous de facto standards like the AT form factor. It was the first major change in desktop computer enclosure, motherboard, and power supply design in many years, improving standardization and interchangeability of parts. The specification defines the key mechanical dimensions, mounting point, I/O panel, power and connector interfaces between a computer case, a motherboard, and a power supply. With the improvements it offered, including lower costs, ATX overtook AT completely as the default form factor for new systems within a few years. ATX addressed many of the AT form factors annoyances that had frustrated system builders. Other standards for smaller boards (including microATX, FlexATX and mini-ITX) usually keep the basic rear layout but reduce the size of the board and the number of expansion slots. In 2003, Intel announced the BTX standard, intended as a replacement for ATX. As of 2009, the ATX form factor remains a standard for do-it-yourselfers; BTX has however made inroads into pre-made systems. This was designed to solve the problems in BAT and LPX Motherboards.

The official specifications were released by Intel in 1995, and have been revised numerous times since, the most recent being version 2.3, released in 2007.

A full-size ATX board is 12 in × 9.6 in (305 mm × 244 mm). This allows many ATX form factor chassis to accept microATX boards as well.