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 Systems, Inc. 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]


MIPS Computer Systems, Inc. was acquired by SGI (Silicon Graphics, Inc) in 1992 and renamed MIPS Technologies, Inc.1
On June 20, 2000 MIPS Technologies, Inc. was divested by SGI becoming its own company.
Imagination Technologies Group plc acquired MIPS Technologies, Inc. November 6, 20122
On September 22, 2017 Imagination Technologies Group plc was acquired by the private equity firm Canyon Bridge Capital Partners. "As part of the deal, Imagination will sell its U.S.-based embedded processor unit MIPS to Tallwood MIPS, a company indeirectly owned by California-based investment firm Tallwood Venture Capital."1


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