Updated: 04/26/2017 by Computer Hope
Commonly called AT and full-size AT, the Full AT is a motherboard form factor introduced by IBM in August 1984, and was widely used in the 1980s. The Full AT is 12" wide x 13.8" deep and only fits into a full size AT tower case. Today, this form factor is rarely found or used and was replaced by ATX and Baby AT. Below is an example of an early IBM AT motherboard.
AT, ATX, Baby AT, Form factor, Motherboard terms, P8 and P9 connector