IRIX (/ˈrɪks/ EYE-ricks) is a discontinued operating system developed by Silicon Graphics (SGI) to run on the company's proprietary MIPS workstations and servers. It is a variety of UNIX System V with BSD extensions. In IRIX, SGI originated the XFS file system and the universally adopted industry-standard OpenGL graphics system.

IRIX desktop.png
IRIX 6.5 Desktop
DeveloperSilicon Graphics
OS familyUnix
Working stateRetired (supported until December 2013)[1]
Source modelClosed source
Initial release1988; 33 years ago (1988)
Final release6.5.30 / 16 August 2006; 14 years ago (2006-08-16)
Marketing targetWorkstations, servers
Kernel typeMonolithic kernel
Default user interfaceIRIX Interactive Desktop

The last major version of IRIX is IRIX 6.5, which was released in May 1998. New minor versions of IRIX 6.5 were released every quarter until 2005; since then there have been four further minor releases. Through version 6.5.22, there are two branches of each release: a maintenance release (identified by an m suffix to the version number) that includes only fixes to the original IRIX 6.5 code, and a feature release (with an f suffix) that includes improvements and enhancements. An overlay upgrade from 6.5.x to the 6.5.22 maintenance release was available as a free download, whereas versions 6.5.23 and higher required an active Silicon Graphics support contract.


SGI first used the IRIX name from the 1988 release 3.0 of the operating system for the SGI IRIS 4D series of workstations and servers. Previous releases are identified only by the release number prefixed by "4D1-", e.g. "4D1-2.2". The 4D1- prefix continued to be used in official documentation to prefix IRIX release numbers.

IRIX 3.x is based on UNIX System V Release 3 with 4.3BSD enhancements, and incorporates the 4Sight windowing system, based on NeWS and IRIS GL. SGI's own Extent File System (EFS) replaces the System V filesystem.[2]

IRIX 4.0, released in 1991, replaces 4Sight with the X Window System (X11R4), the 4Dwm window manager providing a similar look and feel to 4Sight.[2]

IRIX 5.0, released in 1993, incorporates certain features of UNIX System V Release 4, including ELF executables. IRIX 5.3 introduced the XFS journaling file system.

In 1994, IRIX 6.0 added support for the 64-bit MIPS R8000 processor, but is otherwise similar to IRIX 5.2. Later 6.x releases support other members of the MIPS processor family in 64-bit mode. IRIX 6.3 was released for the SGI O2 workstation only.[3] IRIX 6.4 improved multiprocessor scalability for the Octane, Origin 2000, and Onyx2 systems. The Origin 2000 and Onyx2 IRIX 6.4 was marketed as "Cellular IRIX", although it only incorporates some features from the original Cellular IRIX distributed operating system project. IRIX development stabilized with IRIX 6.5, released in 1998. The last version of IRIX is 6.5.30, released in August 2006.

A 2001 Computerworld review found IRIX in a "critical" state. SGI had been moving its efforts to Linux and the Windows-based SGI Visual Workstation but MIPS and IRIX customers convinced SGI to continue to support its platform through 2006.[4] On 6 September 2001, an SGI press release announced the end of the MIPS and IRIX product lines.[5] Production ended on 29 December 2006, with final deliveries in March 2007, except by special arrangement. Support for these products ended in December 2013 and they will receive no further updates.[6]

Much of IRIX's core technology has been open sourced and ported by SGI to Linux, including XFS.

As of 2016, due to the bankruptcy of Silicon Graphics in 2009 and its subsequent purchase by Rackable Systems, which was later purchased by HP Enterprise in 2016, no SGI-badged hardware produced after 2007 is capable of running IRIX, instead designed to run Red Hat Enterprise Linux or SUSE Linux Enterprise Server, based on either IA-64 or x86-64 architecture. HPE has not stated any public plans for IRIX development or source code release.


IRIX 6.5 is compliant with UNIX System V Release 4, UNIX 95, and POSIX (including 1e/2c draft 15 ACLs and Capabilities).[7]

In the early 1990s, IRIX was a leader in Symmetric Multi-Processing (SMP), scalable from 1 to more than 1024 processors with a single system image. IRIX has strong support for real-time disk and graphics I/O. IRIX was widely used for the 1990s and 2000s, in the computer animation and scientific visualization industries due to its large application base and high performance. It still is relevant in a few legacy applications.

IRIX is one of the first Unix versions to feature a graphical user interface for the main desktop environment. IRIX Interactive Desktop uses the 4Dwm X window manager with a custom look designed using the Motif widget toolkit. IRIX is the originator of the industry standard OpenGL for graphics chips and Image processing libraries.

IRIX uses the MIPSPro Compiler for both its front end and back end. The compiler, also known in earlier versions as IDO (IRIS Development Option) was released in many versions, many of which are coupled to the OS version. The last version was 7.4.4m, designed for 6.5.19 or later. The compiler is designed to support parallel POSIX programming in C/C++, Fortran 77/90, and Ada. The Workshop GUI IDE is used for development. Other tools include Speedshop for performance tuning, and Performance Co-Pilot.[8]

Hobbyist useEdit

IRIX has attracted a small but dedicated fanbase of Silicon Graphics hardware enthusiasts who are attracted to various aspects of the operating system and corresponding hardware. This includes the operating system itself, especially its 3D graphics software such as Alias Maya/PowerAnimator and SoftImage, and the HPC elements of the hardware. This hobbyist community is notable for preserving the source code of various in-development versions of Acclaim Entertainment games from a lot discovered in 2017[9] including Turok and NBA Jam.

It is possible to run IRIX version 5.3 through 6.5.22 under emulated Indigo2 and Indy hardware using MAME, being able to emulate the MIPS R4000 CPU, 8 and 24-bit colour depth graphics display and Ethernet card.[10] Reported performance is near 30% the original hardware using mid-end x86-64 CPU.[10]

See alsoEdit


  1. ^ SGI Support of MIPS IRIX Products Continues to December 2013 SGI Services & Support
  2. ^ a b "History of IRIX". Retrieved 2 November 2007.
  3. ^ "SGIstuff : Software : Irix Versions". Retrieved 2 November 2007.
  4. ^ Tom Yager (19 November 2001). "Vital Signs for Unix". Computerworld. Retrieved 6 June 2015.
  5. ^ "SGI - Services & Support: End of General Availability for MIPS IRIX Products". Archived from the original on 19 October 2007. Retrieved 2 November 2007.
  6. ^ "SGI Support of MIPS® IRIX® Products Changes December 2013". Retrieved 3 March 2014.
  7. ^ "IRIX Operating System (Unix)".
  8. ^, SGI IRIX 6.x MIPS
  9. ^ 'Turok' Source Code Will Be Sold on eBay Soon, Thanks to Lucky Warehouse Find
  10. ^ a b "Console Protocols - SGI Emulation". Retrieved 18 April 2021.

External linksEdit