Overview
| Form Factor | Origin | Typical Dimensions | Notes |
|---|---|---|---|
| XT | IBM (1983) | 8.5" x 11" (216 x 279 mm) | Early PC standard, now obsolete. |
| AT | IBM (1984) | 12" x 11" |
Classic full-size format, later replaced by ATX. |
| Baby-AT | IBM era | 8.5" x 10"~13" | Smaller AT-derived design. |
| ATX | Intel (1996) | 12" x 9.6" (305 x 244 mm) | Mainstream desktop standard for years. |
| MicroATX | 1996 | 9.6" x 9.6" (244 x 244 mm) | Smaller ATX, broad compatibility. |
| Mini-ITX | VIA (2001) | 6.7" x 6.7" (170 x 170 mm) | Popular for compact builds. |
| Nano-ITX | VIA (2003) | 120 x 120 mm | Embedded/small systems. |
| Pico-ITX | VIA (2007) | 100 x 72 mm | Very compact embedded format. |
| BTX / MicroBTX / PicoBTX | Intel (2004) | Various | Attempted thermal/layout redesign, limited adoption. |
| DTX / Mini-DTX | AMD (2007) | Up to 200 x 244 mm | Small-form-factor alternatives. |
| Extended ATX (E-ATX) | - | 12" x 13" (305 x 330 mm) | Workstation/server-class boards. |
| NLX / LPX | Intel/OEM era | Various | Used in low-profile systems, mostly legacy. |
| NUC board | Intel (2012) | 100 x 100 mm | Ultra-compact mini PC ecosystem. |
Comparison Images
References
http://gigabytedailycht.blogspot.com/2013/07/blog-post_24.html
Wikipedia motherboard form factor comparison
https://zhuanlan.zhihu.com/p/468200298