[ The PC Guide | Systems and Components Reference Guide | System Case ]

System Case Form Factors

In addition to coming in different styles, cases also come in different form factors. The form factor describes the general layout of the case, the positioning of the slots in the back of the case, and the way that the case matches to the major components that fit into it. In particular, there are three main components that must be matched in terms of their form factor: the case, the power supply, and the motherboard. Usually, when you buy a system case it comes with a power supply, so matching the case and power supply is not a concern, but that is not always the case. In addition, some case form factors can work with more than one power supply form factor.

The most popular case form factors today are the "Baby AT", ATX, and NLX, with the newer microATX/SFX form factor also being used increasingly on lower-end systems. (Baby AT systems are now obsolete but there are so many millions of them in use that they remain a factor, especially in the upgrade and repair market.) These cases are not interchangeable, since they are shaped differently, and require motherboards with a different form factor. If you are building your own system you must ensure your motherboard and case/power supply form factors match. There are cases that can handle both baby AT and ATX motherboards.

Note: Not all case styles are available in all form factors. Increasingly, as "Baby AT" loses in popularity to ATX and its variants, many newer cases are becoming hard to find in the Baby AT format. The older form factors (PC/XT, and AT) are not used in modern systems at all.

Next: PC/XT Form Factor

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