MIPS OS

MIPS OS is the operating system first used with the MIPS microprocessor that debuted in 1985. It was more generally known as RISC/os. MIPS OS was a Unix variant that loosely descended from 4.2BSD, System V Release 3 and System V Release 4 Unix'es. MIPS OS was one of the first 32-bit operating systems for RISC-based workstation-class computers. It was also on of the first 64-bit Unix releases for RISC based microprocessors, with the first 64-bit versions appearing in 1990. MIPS OS supported full 32-bit and 64-bit applications simultaneously using the underlying hardware architecture supporting the MIPS-IV instruction set.

The MIPS OS, originally developed by MIPS Computer Systems Inc. in 1985, was originally used on the MIPS Computer Systems' own line of workstations. It was a dual-universe operating system, meaning that it had separate, switchable runtime environments to closely model both the BSD and System V flavors of Unix. It was arguably a successful concept, but it never really gained widespread acceptance, and the MIPS OS itself never ran on any platforms other than MIPS' own workstations. In spite of the failure of MIPS' to sell workstations in quantity, MIPS OS development continued steadily with product releases and upgrades including adding support for System V Release 4, R6000 processor support and later SMP support on the R4400 and R6000 processors.

During the early 1990s, several vendors including DEC, Silicon Graphics, and Ardent licensed portions of the software MIPS had written for the MIPS OS for their own Unix variants. MIPS' influence was most visible as the C compiler and development tools shared by virtually all commercial Unixes for the MIPS processor, the low memory operating system code, and the ROM code for MIPS processors.

In July 1992, Silicon Graphics purchased MIPS Computer Systems for $220M. With Ardent/Stardent/Kubota disappearing during the 1990s and DEC moving to OSF/1 and then Tru64 before being bought out by Compaq (later Hewlett-Packard), pieces of the MIPS OS legacy were incorporated into IRIX, which runs on the MIPS based SGI workstations.