RISC Technology Personal Computer.
(Commonly, but incorrectly, known as the "PC-RT", later changed to just "RT") IBM's first RISC-based Unix computer. The RT-PC was the predecessor to IBM's RS/6000. It ran AIX 1.x and 2.x and had a PC-AT bus and IBM's ROMP microprocessor. It was withdrawn from the marketing around 1989 or 1990.