Hardware Reference
In-Depth Information
came in a case that was identical except for slot bracketry and the lack of a hole for the
cassette port. Eventually, the XT motherboard design became popular, and many other
PC motherboard manufacturers of the day copied IBM's XT design and produced similar
boards.
Full-Size AT
The full-size AT motherboard form factor matches the original IBM AT motherboard
design. This allows for a large board of up to 12 inches wide by 13.8 inches deep. The
full-size ATboardfirstdebutedinAugust1984,whenIBMintroduced thePersonal Com-
puter AT (advanced technology). To accommodate the 16-bit 286 processor and all the
necessary support components at the time, IBM needed more room than the original PC/
XT-sized boards could provide. So for the AT, IBM increased the size of the motherboard
butretainedthesamescrewholeandconnectorpositionsoftheXTdesign.Toaccomplish
this, IBM essentially started with a PC/XT-sized board and extended it in two directions
(see
Figure 4.3
).
Figure 4.3
IBM AT motherboard (circa 1984).
