The
IBM Personal Computer AT, more commonly known as the
IBM AT and also sometimes called the
PC AT or
PC/AT, was
IBM's second-generation
PC, designed around the 6 MHz
Intel 80286 microprocessor and released in 1984 as System Unit
5170. The name
AT stood for "Advanced Technology", and was chosen because the AT offered various technologies that were then new in personal computers; one such advancement was that the 80286 processor supported
protected mode. IBM later released an 8 MHz version of the AT.