microATX

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Computer form factors	PCB Size (mm)
WTX	356×425
AT	350×305
Baby-AT	330×216
BTX	325×266
ATX	305×244
LPX	330×229
NLX	254×228
microATX	244×244
DTX	244×203
FlexATX	229×191
Mini-DTX	203×170
EBX	203×146
microATX (Min.)	171×171
Mini-ITX	170×170
EPIC (Express)	165×115
Nano-ITX	120×120
COM Express	125×95
ETX / XTX	114×95
Pico-ITX	100×72
PC/104(-Plus)	96×90
microETXexpress
nanoETXexpress
mobile-ITX	75×45

The A8N VM CSM, an ASUS microATX motherboard

microATX, also known as µATX (sometimes transliterated as mATX^[1] or uATX^[2]^[3] 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 uATX boards can be as small as 6.75 inches by 6.75 inches (171.45 mm x 171.45 mm)^[4]. 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.

1 Backward-compatibility
2 Expandability
3 References
4 External links

[edit] 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,^[5] 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.

[edit] Expandability

Most modern ATX motherboards have five or more PCI or PCI-Express expansion slots, while microATX boards typically have only three (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 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.

[edit] References

^ See this thread on HardForum.com for an example of "mATX."
^ Intel Developer Forum
^ See this thread for an example of "uATX."
^ Intel&reg Desktop Board D201GLY Overview
^ 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.