MicroATX

microATX, also known as µATX (sometimes transliterated as mATX [See [http://www.hardforum.com/showthread.php?t=1157067 this thread] on HardForum.com for an example of "mATX."] or uATX [http://www.prcidf.com.cn/en/training/technology_session.html Intel Developer Forum ] ] See [http://discussions.virtualdr.com/archive/index.php/t-98202.html this thread] for an example of "uATX."] on online forums) is a small form factor standard for computer motherboards, with a maximum size of 9.6 inches x 9.6 inches (244 mm x 244 mm), but some microATX boards can be as small as 6.75 inches by 6.75 inches (171.45 mm x 171.45 mm) [http://www.intel.com/products/motherboard/D201GLY/index.htm Intel® Desktop Board D201GLY Overview ] (In Intel® Technical Specifications this board (and others with dimensions 171.45 mm x 171.45 mm) named as "Mini-ITX, compatible with microATX", although standard size for mini-ITX boards is 170 mm x 170 mm)] . The standard ATX size is 25% longer, at 305 mm × 244 mm (12" wide x 9.6" deep).

Currently available microATX motherboards support CPUs from VIA, Intel or AMD.

Backward-compatibility

microATX was explicitly designed to be backward-compatible with ATX. The mounting points of microATX motherboards are a subset of those used on full-size ATX boards, and the I/O panel is identical. Thus, microATX motherboards can be used in full-size ATX cases. Furthermore, most microATX motherboards generally use the same power connectors as ATX motherboards, [As of 2007, most motherboards follow the ATX12V 2.2 specification, which provides for a 24-pin main power connector, and a 4-pin auxiliary connector.] thus permitting the use of full-size ATX power supplies with microATX boards.

microATX boards often use the same chipsets (northbridges and southbridges) as full-size ATX boards, allowing them to use many of the same components. However, since microATX cases are typically much smaller than ATX tower cases, they usually have fewer I/O ports and expansion slots.

The smaller case allows for portability and is a space saving case. It has also been used in creative projects such as NES PCs.

Expandability

Most modern ATX motherboards have five or more PCI or PCI-Express expansion slots, while microATX boards typically have only four (four being the maximum permitted by the specification). In order to conserve expansion slots and case space, many manufacturers produce microATX motherboard with a full-range of integrated peripherals (especially integrated graphics), which may serve as the basis for small form factor and media center PCs. For example, the Asus [http://www.asus.com/products4.aspx?l1=3&l2=15&l3=210&model=766&modelmenu=1 A8N-VM CSM] motherboard (pictured right) features onboard GeForce 6 graphics, AC97 audio, and gigabit Ethernet (among others), thus freeing up the expansion slots that would have been used for a graphics card, sound card, and Ethernet card.

In addition, some microATX cases require the use of Low-Profile PCI cards and use power supplies with non-standard dimensions.

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