This document provides an overview of the Micro ATX motherboards for personal computers.
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Saturday, October 19, 2013 6:14 PM
The Micro ATX Motherboard
microATX is a motherboard form factor Intel introduced in December 1997 as an evolution of the ATX form factor for smaller and lower-cost systems. The reduced size compared to standard ATX allows for a smaller chassis, motherboard, and power supply, thereby reducing the cost of the entire system. The microATX form factor is also backward-compatible with the ATX form factor and can be used in full-size ATX cases. Of course, a microATX case doesn’t take a full-size ATX board. This form factor has become popular in the low-cost PC market. Currently, mini-tower chassis systems dominate the low-cost PC market, although their small sizes and cramped interiors severely limit future upgradeability.
The main differences between microATX and standard or Mini-ATX are as follows:
Reduced width motherboard (9.6 inches [244mm] instead of 12 inches [305mm] or 11.2 inches [284mm])
Fewer I/O bus expansion slots (four maximum, although most boards feature only three)
Smaller power supply optional (SFX/TFX form factors)
The microATX motherboard maximum size is only 9.6 inches×9.6 inches (244mm×244mm) as compared to the full-size ATX size of 12 inches×9.6 inches (305mm×244mm) or the Mini-ATX size of 11.2 inches×8.2 inches (284mm×208mm). Even smaller boards can be designed as long as they conform to the location of the mounting holes, connector positions, and so on, as defined by the standard. Fewer slots aren’t a problem for typical home or small-business PC users because more components such as sound and video are usually integrated on the motherboard and therefore don’t require separate slots. This higher integration reduces motherboard and system costs. External buses, such as USB, 10/100/1000 Ethernet, and optionally 1394 (FireWire), can provide additional expansion out of the box. The specifications for microATX motherboard dimensions are shown in Figure 4.16.
The microATX form factor is similar to ATX for compatibility. The similarities include the following:
Standard ATX power connectors
Standard ATX I/O panel
Mounting holes and dimensions are a subset of ATX
These similarities ensure that a microATX motherboard can easily work in a standard ATX chassis with a standard ATX power supply, as well as the smaller microATX chassis and SFX/TFX power supply.
The overall system size for a microATX is small. A typical case is only 12–14 inches tall, about 7 inches wide, and 12 inches deep. This results in a kind of micro-tower or desktop size. A typical microATX motherboard is shown in Figure 4.17.
Figure 4.17. A typical microATX motherboard’s dimensions are 9.6 inches×9.6 inches.
As with ATX, Intel released microATX to the public domain to facilitate adoption as a de facto standard. The specification and related information on microATX are available through the Desktop Form Factors site (www.formfactors.org).