In 1981 Dr. John L. Hennessy of Stanford University began design work on a RISC CPU. A group lead by Hennessy left Stanford in 1984 to found MIPS Computer System (renamed MIPS Technologies in 1992;1 bought by Imagination Technologies November 6th, 2012).2 MIPS' first workstation the M/5003 was introduced in 1986 and featured the company's first RISC CPU, the R2000.4 The operating system for MIPS' M/500 workstation was named UMIPS (MIPS UNIX).5


UMIPS was "MIPS Computers' first operating system, a port of Berkeley's BSD4.3 version of UNIX." 6 4.3BSD was released in June of 19867 with MIPS receiving the source in July, and shipping the M/500 with UMIPS by October of the same year.8 Version 1.1 was the first version of UMIPS to System V R3 environmentv1.1 With the introduction of AT&T UNIX System V Release 3 in 19879, version 1.1 of UMIPS became; in Unix parlance, dual-universe.


UMIPS-BSD, also known as UMIPS/BSD,


UMIPS-V, also known as UMIPS/V, UMIPS_V, or UMIPS (System V) was a port of AT&T UNIX System V Release 3. this February 1989 Security Digest Archive thread where a user complains about poor performance from HP-UX 3.0 when compared to other Unices at his location, including "UMIPS 3.10." UMIPS 3.10C referred to as RISC/os [footnote]


"RISC/os (UMIPS)," fully known as "MIPS System VR3, RISC/os" was "a derivative of UNIX System V Release 3," and "also one of the roots of IRIX."[footnote] Presumably the other root or roots of IRIX being IRIS GL and/or GL2-W. "MIPS System VR3, RISC/os, and Irix" "are all ways of referring to the same basic operating system, a derivative of UNIX System V Release 3."[SeeMipsRunP452] Silicon Graphics first MIPS-based workstation the Professional Iris 4D/60, featured a MIPS R2300 board (motherboard & CPU) and not a Silicon Graphics IP board. It is suggested here that "Early releases of IRIX were nothing more than "RISC/os (UMIPS)," with added support for Silicon Graphics' graphics hardware. RISC/os 4.x was distributed on one to two QIC-24 tapes[footnote]


  • UMIPS 1.x
    • UMIPS-BSD 1.0
    • UMIPS 1.1
  • RISC/os 4.x (based on AT&T System V Release 3)
    • RISC/os 4.0
    • RISC/os 4.01
    • RISC/os 4.02
    • RISC/os 4.10
    • RISC/os 4.20
    • RISC/os 4.30
    • RISC/os 4.50 (June 1990)
    • RISC/os 4.50B
    • RISC/os 4.51 (August 1990)
    • RISC/os 4.52
    • RISC/os 4.52B
    • RISC/os 4.52B2[footnote]
    • RISC/os 4.52C
  • RISC/os 5.x based on AT&T System V Release 4
    • RISC/os 5.0 (late '91 early '92)
    • RISC/os 5.00B
    • RISC/os 5.01


EP/IX was "the CDC implementation of Unix for the Control Data 4000 series of computers."[footnote] and "an extension to/derivative of RISC/os."


ES/os was "a variant of RISC/os 4.52 with extra device drivers, a few bug fixes, etc." produced by Evans & Sutherland [footnote]


SEIUX, from Sumitomo Electric Industries was "mostly a clone of the RISC/os," "even binary compatible with RISC/os," and "should be very much like RISC/os 4." [footnote]


RISCwindows (Xmips) was the name of MIPS' implementation of the X Window System for its RISC/os. Initially RISCwindows used TWM (Tab/Tom's Window Manager)[21] Window Managers MWM (Motif Window Manager), RISCwindows 3.x including TWM (Tab/Tom's Window Manager)[21] Like RISC/os itself, RISCwindows 4.0 was distributed on a QIC tape[footnote]
  • RISCwindows 3.x
    • RISCwindows 3.00 (introduced 4th quarter of 1989 or 1st quarter or 1990)[20]
    • RISCwindows 3.10 (introduced 2nd quarter of 1990)
    • RISCwindows 3.11
    • RISCwindows 3.21[22]
  • RISCwindows 4.x
    • RISCwindows 4.00 (built with Motif 1.1.1)[footnote]
    • RISCwindows 4.10 (X11R4, built with Motif 1.1.1)[footnote]
    • RISCwindows 4.11


Control Data Corporation (later Control Data Systems)

Evans & Sutherland

MIPS Computer Systems[footnote]

  • MIPS M/500
  • MIPS M/800
  • MIPS M/1000
  • MIPS M/120 (Special thanks to Unknown)
  • MIPS M/120-3
  • MIPS M/120-5
  • MIPS M/2000
  • MIPS RS2030
  • MIPS RC2030
  • MIPS RC3240 (Special thanks to Miod Vallat)
  • MIPS RS3230
  • MIPS 'Magnum 3000' RC3230 (Special thanks to Miod Vallat)
  • MIPS RC3260
  • MIPS RC3330 (Special thanks to Walter Belgers)
  • MIPS RC3360
  • MIPS RC6260
  • MIPS RC6280
  • MIPS RC6380-100
  • MIPS RC6380-200
  • MIPS RC6380-400
  • MIPS RS4330
  • MIPS RS4340
  • MIPS RS4440
  • MIPS RC4370
  • MIPS RC4470

Sumitomo Electric Company

Whitechapel Workstations Ltd.[footnote]


About Taygeta, Taygeta Scientific Inc.
Giga's Computer Museum
Mips RC 3230 (Magnum 3000)
NO-L.ORG: The risc/OS Repository
Richard Geiger: Resume
Toru Nishimura: MIPS and SGI relationship
XConsortium modifications for UMIPS