The Free On-line Dictionary of Computing (30 December 2018):

RT-PC

    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  It was withdrawn from the marketing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.

   (1995-04-06)