What is atx?

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.

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Some articles on atx:

ATX - Power Supply - Issues With Dell Power Supplies
... While the motherboard connectors appear to be standard ATX, and will actually fit a standard power supply, they are not compatible ... The change affects not only 20-pin ATX connectors, but also auxiliary 6-pin connectors ... Modern Dell systems might use standard ATX connectors ...
Flex ATX
... is a motherboard form factor derived from ATX ... motherboard mounting holes required for microATX and the same I/O plate system as ATX and microATX ... used also for the form factor of a PSU that is smaller than a standard ATX PSU and is used in small cases that host a FlexATX or Mini ITX motherboard or in thin rackmount servers such as 1U racks ...
Super Robot Wars Original Generation: Divine Wars - Media - Manga
... Meanwhile Super Robot Wars Divine Wars - Record of ATX (スーパーロボット大戦OG ディバイン・ウォーズ Record of ATX?) is manga series by Tatsunosuke Yatsufusa that tells a similar story but from the ...
BTX (form Factor)
... motherboards, originally intended to be the replacement for the aging ATX motherboard form factor in late 2004 and early 2005 ... on motherboards compliant with the circa-1996 ATX specification ... The ATX and BTX standards were both proposed by Intel ...
AMD 690 Chipset Series - List of Mainboards Using 690 Chipset
... Yes Yes DDR2 SO-DIMM ASUS M2A-VM Micro ATX No Yes DVI M2A-VM HDMI addon card Yes DVI-D, VGA, FireWire 1394a, add-on card HDMI, S-Video, YPbPr ...