Physical form factor
Form factor size chart
The motherboard fits into the computer case with screws or clips. There are many form factors, or sizes of motherboard. In general, it is necessary for the case, power supply, and motherboard to conform to the same standard in order for them to operate properly.
* XT (8.5 × 11" or 216 × 279 mm) - obsolete - see XT bus architecture
* AT (12 × 11"–13" or 305 × 279–330 mm) - obsolete - see AT bus architecture
* Baby-AT (8.5" × 10"–13" or 216 mm × 254-330 mm)
* ATX (Intel 1996; 12" × 9.6" or 305 mm × 244 mm)
* EATX (12" × 13" or 305mm × 330 mm)
* Mini-ATX (11.2" × 8.2" or 284 mm × 208 mm)
* microATX (1996; 9.6" × 9.6" or 244 mm × 244 mm) - fewer slots than ATX, so can use smaller PSU
* LPX (9" × 11"–13" or 229 mm × 279–330 mm) - in slimline retail PCs
* Mini-LPX (8"–9" × 10"–11" or 203–229 mm × 254–279 mm) - in slimline retail PCs
* NLX (Intel 1999; 8"–9" × 10"-13.6" or 203–229 mm × 254–345 mm) - coming soon; requires add-in card riser
* FlexATX (Intel 1999; 9.6" × 9.6" or 244 × 244 mm max.) - can be smaller than microATX
* Mini-ITX (VIA Technologies 2003; 6.7" × 6.7" or 170 mm × 170 mm max.; 100W max.)
* Nano-ITX (VIA Technologies 2004; 120 mm × 120 mm max.)
* BTX (Intel 2004; 12.8" × 10.5" or 325 mm × 267 mm max.)
* MicroBTX (Intel 2004; 10.4" × 10.5" or 264 mm × 267 mm max.)
* PicoBTX (Intel 2004; 8.0" × 10.5" or 203 mm × 267 mm max.)
* WTX (Intel 1998; 14" × 16.75" or 355.6 mm × 425.4 mm)
* ETX and PC/104, used in embedded systems.