atx

ATX (Advanced Technology eXtended) is a motherboard and power supply configuration specification developed by Intel in 1995 to improve on previous de facto standards like the AT design. 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 dimensions; the mounting points; the I/O panel; and the power and connector interfaces among a computer case, a motherboard, and a power supply.
ATX is the most common motherboard design. Other standards for smaller boards (including microATX, FlexATX, nano-ITX, and mini-ITX) usually keep the basic rear layout but reduce the size of the board and the number of expansion slots. Dimensions of a full-size ATX board are 12 × 9.6 in (305 × 244 mm), which allows many ATX chassis to accept microATX boards. The ATX specifications were released by Intel in 1995 and have been revised numerous times since. The most recent ATX motherboard specification is version 2.2. The most recent ATX12V power supply unit specification is 2.53, released in June 2020. EATX (Extended ATX) is a bigger version of the ATX motherboard with 12 × 13 in (305 × 330 mm) dimensions. While some dual CPU socket motherboards have been implemented in ATX, the extra size of EATX makes it the typical form factor for dual socket systems, and with sockets that support four or eight memory channels, for single socket systems with a large number of memory slots.
In 2004, Intel announced the BTX (Balanced Technology eXtended) standard, intended as a replacement for ATX. Some manufacturers introduced the new standard; however, in 2006 Intel discontinued any future development of BTX. As of 2021, the ATX design still remains the de facto standard for personal computers.

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