aTx

ATX, short for Advanced Technology Extended, is a motherboard form factor widely used in consumer desktop computers. Introduced by Intel in 1995 as a successor to the AT standard, ATX standardized the layout of the motherboard, power, and I/O so components from different vendors could interoperate more easily. The form factor remains the dominant standard for desktop PCs.

Key specifications include its physical size of 12 inches by 9.6 inches (305 by 244 mm). The layout places the CPU and memory near the top, expansion slots along the lower edge, and the I/O panel at the back. A defining feature is the standardized power supply connector: a 24-pin main power connector, with additional 4- or 8-pin 12V connectors used to supply power to the CPU and other components. Front-panel and peripheral connectors follow a consistent pinout, enabling easier assembly and upgrades.

ATX has several variants. MicroATX, at 9.6 by 9.6 inches, offers a smaller footprint while remaining compatible with many ATX cases and power supplies. Extended ATX (E-ATX) increases the board size to accommodate more expansion slots and features, requiring larger cases. While ATX boards fit in most ATX-compatible cases, E-ATX boards require taller or larger enclosures.

Impact and evolution: ATX established widely adopted standards for motherboard mounting points, I/O shield alignment, and power delivery, contributing to greater interoperability among components. It remains prevalent in desktop computing, even as smaller form factors and newer power architectures continue to emerge. See also: microATX, E-ATX, ITX, PCIe, EPS.