MicroATX

microATX, also known as µATX (sometimes transliterated as mATX^[1] or uATX^[2][3] on internet forums) is a small form factor standard for motherboards that was introduced in December of 1997.^[4] The maximum size of a microATX motherboard is 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)^[5]. 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,^[6] 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 cases, they usually have fewer expansion slots.

Expandability

ATX motherboard size comparison.     FlexATX (229x191mm)     MicroATX/Embedded ATX (244x244mm)     Mini ATX (284x208mm)     Standard ATX (305x244mm)     Extended ATX (EATX) (305x330mm)     Workstation ATX (WATX) (356x425mm)

The A8N VM CSM, an ASUS microATX motherboard

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 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 recent years, however, it is common even for ATX boards to integrate all these components, as much of this functionality is contained in the typical northbridge/southbridge pair. With the "must-have" functions already present on the motherboard, the need for having many expansion slots has faded, and adoption of microATX has increased even to be used in ATX cases.

A more modern limitation of a microATX case is due to its reduction in drive bays. Current southbridges support up to six SATA devices, in addition of up to four legacy IDE devices. The full range of connectors are commonly found on microATX boards, and can be fully exploited if the board is mounted in an ATX case.

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

References

External links

• "microATX Motherboard Interface Specification" (in English) (PDF). Intel Corporation. pp. 23. http://www.formfactors.org/developer/specs/matxspe1.2.pdf. Retrieved on 2006-09-10.