Editing MIPS RISC/os (section)

{{distinguish|text=[[RISC OS]], an operating system for ARM processors originally developed by Acorn Computers}}
{{refimprove|date=December 2017}}
{{Infobox OS
| name                   = RISC/os
| logo                   = 
| screenshot             = 
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| developer              = [[MIPS Technologies|MIPS Computer Systems, Inc.]]
| source_model           = 
| kernel_type            = 
| supported_platforms    = [[MIPS architecture]]
| ui                     = 
| family                 = [[Unix]]
| released               = 
| latest_release_version = 
| latest_release_date    = 
| latest_test_version    = 
| latest_test_date       = 
| marketing_target       = 
| programmed_in          = 
| prog_language          = 
| language               = 
| updatemodel            = 
| package_manager        = 
| working_state          = Discontinued
| license                = 
| website                = 
}}

'''RISC/os''' is a discontinued [[Unix|UNIX]] [[operating system]] developed by [[MIPS Technologies|MIPS Computer Systems, Inc.]] from 1985 to 1992, for their computer [[workstation]]s and [[server (computing)|server]]s, including such models as the MIPS M/120 server and [[MIPS Magnum]] workstation.<ref name="mips_product_overview">{{ cite book | url=https://archive.org/details/bitsavers_mipsbrochuiew1990_3211603/mode/1up | title=MIPS Product Overview | publisher=MIPS Computer Systems, Inc. | date=1990 | access-date=3 March 2022 }}</ref> It was also known as '''UMIPS''' or '''MIPS OS'''.<ref name="thoryk">{{Cite web |url=http://ryan.tliquest.net/sgi/irix_versions.html#MIPS |title=History of IRIX, by Ryan Thoryk |access-date=2008-07-16 }}</ref>

RISC/os was mainly based on [[UNIX System V]] with additions from [[Berkeley Software Distribution|4.3BSD]] UNIX, ported to the [[MIPS architecture]]. It was a "[[Universe (Unix)|dual-universe]]" operating system, meaning it had separate, switchable runtime environments that were compatible with either [[System V Release 3]] or [[4.3BSD]].<ref name="thoryk"/> MIPS OS was one of the first [[32-bit]] operating systems for [[RISC]]-based workstation-class computers. It was also one 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. Later releases added support for [[System V Release 4]] compatibility,<ref name="thoryk"/> [[R6000]] processor support and later [[symmetric multiprocessing]] support on the [[R4000#R4400|R4400]] and R6000 processors.

During the early 1990s, several vendors including [[Digital Equipment Corporation|DEC]], [[Silicon Graphics]], and [[Ardent Computer|Ardent]] licensed portions of the software MIPS had written for the RISC/os for their own Unix variants.{{citation needed|date=September 2010}}  [[Evans & Sutherland]] licensed RISC/os directly for its ESV series workstations.  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.{{citation needed|date=September 2010}}

Because of its early UNIX heritage, RISC/os was limited in comparison to modern UNIX variants{{snd}} for example, even the last releases of RISC/os did not support [[library (computing)|shared libraries]].{{Citation needed|date=July 2008}}

In July 1992, Silicon Graphics purchased MIPS Computer Systems for $220M. Support for RISC/os was subsequently phased out.<ref name="thoryk"/>