AT form factor

From Wikipedia, the free encyclopedia

The AT form factor is the first modern form factor to be widely used. AT (Advanced Technology) was released in 1984 by IBM. Unlike the PC and XT form factors that preceded it, AT became a widely used design as a result of the booming home computer market in the 1980s. IBM clones made at the time began using AT compatible designs, contributing to its popularity. In the 1990s many computers still used AT and its variants, but ATX has been the most popular standard since 1997.

[edit] Design

Main article: Industry Standard Architecture

AT was not a very large technological jump from older form factors. The AT's largest advancement was its "tower" design and a remote power switch in the front. The AT power supply provided 192 watts, triple that of older form factors.

The AT motherboard is 12 inches (305 mm) which means it will not fit in "mini desktop" or "minitower cases". The board's size also means that it takes up space behind the drive bays making installation of new drives more difficult. The power connectors for AT motherboards are two nearly identical 6-pin cords. Unfortunately, the two power connectors it requires are not easily distinguishable, leading many people to damage their boards when they were misconnected. However, technicians need only remember the phrase "black wires together in the middle" or "red and red and you are dead" to prevent this. The two black wires on either connector must be plugged in back to back, creating a row of 4 black cords (out of the total 12) and a correct connection.

[edit] Variants

In 1985 IBM introduced Baby AT'. Soon after all computer makers abandoned AT for the cheaper and smaller Baby AT. These motherboards have the same functionality as ATs but are 2" (51 mm) narrower and marginally longer. Although the Baby AT form factor is obsolete, a few computers are still using it, and modern PC cases are generally backwards compatible to fit Baby AT.

In 1995 Intel introduced ATX, a modern form factor which has quickly replaced older Baby AT computers.