Early PCs used the AT form factor and 12in wide motherboards. The sheer size of an AT motherboard caused problems for upgrading PCs and did not allow use of the increasingly popular slimline desktop cases. These problems were largely addressed by the smaller version of the full AT form factor, the Baby AT, introduced in 1989. Whilst this remains a common form factor, there have been several improvements since.
All designs are open standards and as such don’t require certification. A consequence is that there can be some quite wide variation in design detail between different manufacturers\’ motherboards. However, keeping to the standards allows case manufacturers to develop for particular motherboard form factors, a boon for home builders, modders and PC technicians.
The table below shows common motherboard form factors in use.
Table of Common Form Factors
| Name | PCB Size (mm) |
|---|---|
| AT | 350×305 |
| ATX | 305×244 |
| Baby-AT | 330×216 |
| BTX | 325×266 |
| COM Express | 125×95 |
| DTX | 244×203 |
| EBX | 203×146 |
| EPIC (Express) | 165×115 |
| ESMexpress | 125×95 |
| ETX / XTX | 114×95 |
| FlexATX | 229×191 |
| LPX | 330×229 |
| microATX | 244×244 |
| microATX (Min.) | 171×171 |
| Mini-DTX | 203×170 |
| Mini-ITX | 170×170 |
| mobile-ITX | 75×45 |
| Nano-ITX | 120×120 |
| NLX | 254×228 |
| PC/104 (-Plus) | 96×90 |
| Pico-ITX | 100×72 |
| WTX | 356×425 |
- Evolution of the motherboard
- BIOS – What motherboard BIOS does for a PC
- CMOS – complementary metal oxide silicon – RAM chips on motherboards
- EFI – Extensible Firmware Interface – explained
- Motherboard form factors
- Baby AT (BAT) Motherboard Form Factor
- LPX – Low Profile eXtension motherboard form factor
- ATX form factor
- NLX – New Low profile eXtended – form factor for motherboards
- Micro ATX motherboard form factor
- FlexATX motherboard form factor
- BTX – Balanced Technology eXtended – Motherboard Form Factor
- Riser architectures for motherboards
- CPU interfaces – motherboard slots and sockets for AMD and Intel processors