MIPS OS is the operating system first used with the MIPS microprocessor that debuted in 1985. MIPS OS is a Unix variant that loosely descended from 4.2BSD Unix. MIPS OS was one of the first 32-bit operating systems for RISC-based workstation-class computers.
The MIPS OS, originally developed by MIPS Computer Systems Inc, was used on the Ardent Titan, DEC DECstation 3100, and later on Silicon Graphics workstations. In 1987, Silicon Graphics switched from the Motorola 68000 architecture to the MIPS architecture and adopted the MIPS OS to its new line of graphical workstations, the 4D series, and renamed its version of MIPS OS to IRIX. In 1992, Silicon Graphics purchased MIPS Computer Systems.
With Ardent/Stardent disappearing during the 1990s and DEC moving to OSF/1 and then Tru64 before being bought out by Compaq (later Hewlett-Packard), the legacy of the MIPS OS has been IRIX, which is still used on SGI workstations to date.
