RISC/OS

RISC/OS, also known as UMIPS was an early BSD and System V-based UNIX produced by MIPS Computer Systems. Beginning as a 4.3BSD port in 1986, it evolved into a dual-universe System V/4.3BSD UNIX and later formed one of the core codebases folded into SGI’s 4D1/IRIX, Unlike GL2, RISC/OS had roots in both BSD and System V. When SGI purchased MIPS Computer Systems, it was quickly phased out and 4D1-3.x and later IRIX 4.0 were offered as successors.

History

UMIPS 1.0 was a crude 4.3BSD port shipped with the MIPS M/500 systems in late 1986. As AT&T released System V R3 (1987), MIPS added System V compatibility and a dual-universe mode so administrators and users could select BSD or System V behavior for their system codebase (separate command sets, libraries, headers, etc.). Over time the UMIPS name gave way to the RISC/os brand for later releases. The final release was offered in 1992.

RISCwindows

This was the UMIPS and RISC/os GUI, consisting of an X11 port and uwm (Ultrix Window Manager) and optionally Motif.

Known Derivatives

Both MIPS Computer Systems hardware and software were rebranded and licensed by OEMs, resulting in Control Data and Evans and Sutherland branded hardware, and EP/IX and SEIUX, which both borrowed and retained some compatibility with RISC/os.

Version History

• UMIPS 1.0 (1986) — 4.3BSD port, shipped with early M/500 systems.
• UMIPS 1.1 (late 1980s) — dual-universe (BSD + System V) support added.
• UMIPS 2.x / 3.x — continued development; by UMIPS 3.10 the RISC/os name was already being used informally.
• RISC/os 4.x (late 1980s — 1990) — formal RISC/os series based on System V Release 3.
• RISC/os 5.x (1991) — based on System V Release 4; RISC/os 5.0 released October 28, 1991. This was the final version of RISC/os as SGI discontinued it in 1992.