IBM PC AT AT PC AT <computer> ("Advanced Technology") A version of the {IBM PC}, released in Aug 1984 with an {Intel 80286} processor, a 16-bit {bus}, a medium-speed {hard disk} and a 1.2 {megabyte} {floppy} {disk drive}. It had a larger case than the PC, which allowed it to accept "{tall cards}". The AT keyboard corrected the PC's non-standard placement of the {return} and left shift keys but shortened the {backspace} key, making it harder to reach. (1995-03-01)