Stands for "Advanced Technology eXtended." ATX is a motherboard specification that defines the board's physical dimensions, connector placement, I/O ports, and supported power supplies. It was introduced by Intel in 1995 and was designed to replace the previous "AT" standard for desktop PCs. Since then, many variations of the original ATX standard have been developed and some are still used in today's desktop computers.

There are several distinct differences between ATX and the AT form factor it superseded. For example, ATX has an I/O panel that is twice the height of the AT panel and allows for flexible interface layouts. It also has different processor, memory, and drive I/O locations. These changes provide the following benefits:

  • Fewer cables
  • Improved reliability
  • Support for modern I/O standards like USB
  • Support for integrated graphics
  • Larger expansion slots
  • Easier processor and memory upgrades
  • Reduced cost

A full size ATX motherboard is 12 inches wide and 9.6 inches deep (305 x 244 mm). There are also several variants of ATX, which have slightly different form factors. This include the following:

  • FlexATX – 9 × 7.5 in (229 × 191 mm)
  • MicroATX – 9.6 × 9.6 in (244 × 244 mm)
  • Mini ATX – 11.2 × 8.2 in (284 × 208 mm)
  • Extended ATX (EATX) – 12 × 13 in (305 × 330 mm)
  • Workstation ATX (WTX) – 14 × 16.75 in (356 × 425 mm)

The ATX specification defines the mounting hole locations, which means any standard ATX motherboard can be attached to any standard ATX case. Smaller boards (such as FlexATX, MicroATX, and Mini ATX) have several of the same mounting hole locations, so they can be placed in a standard ATX case as well. The universal compatibility of ATX boards and components make them a popular choice for hobbyists who build their own PCs.

Updated December 4, 2014

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