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IRIX desktop.png
IRIX 6.5 Desktop
Developer Silicon Graphics
OS family Unix
Working state Retired (supported until December 2013)[1]
Source model Closed source
Initial release 1983; 33 years ago (1983)
Final release 6.5.30 / August 16, 2006; 9 years ago (2006-08-16)
Marketing target Workstations, servers
Platforms MIPS
Kernel type Monolithic kernel
Default user interface IRIX Interactive Desktop
License Proprietary
Official website

IRIX is a discontinued operating system developed by Silicon Graphics (SGI) to run natively on their MIPS workstations and servers. It is based on UNIX System V with BSD extensions. IRIX was the first operating system to include the XFS file system.

The last major version of IRIX was 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 were two branches of each release: a maintenance release (identified by an m suffix to the version number) that included only fixes to the original IRIX 6.5 code, and a feature release (with an f suffix) that included improvements and enhancements. An overlay upgrade from 6.5.x to the 6.5.22 maintenance release is available as a free download, whereas versions 6.5.23 and higher require an active Silicon Graphics support contract, despite only running on Silicon Graphics hardware.


The IRIX name was first used around the time of release 3.0 of the operating system for SGI's IRIS 4D series of workstations and servers, in 1988. Previous releases were 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 was based on UNIX System V Release 3 with 4.3BSD enhancements, and incorporated the 4Sight windowing system, based on NeWS and IRIS GL. SGI's own Extent File System (EFS) replaced the System V filesystem.[2]

IRIX 4.0, released in 1991, replaced 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, incorporated certain features of UNIX System V Release 4, including ELF executables.[3] IRIX 5.3 introduced the XFS journaling file system.

In 1994, IRIX 6.0 added support for the 64-bit MIPS R8000 processor, but was otherwise similar to IRIX 5.2. Later 6.x releases supported other members of the MIPS processor family in 64-bit mode. IRIX 6.3 was released for the SGI O2 workstation only.[4] 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 incorporated some features from the original Cellular IRIX distributed operating system project.[5] IRIX development stabilized with IRIX 6.5, released in 1998. The last version of IRIX was 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 Windows,[a] but MIPS/IRIX customers had forced it to continue to support that platform through 2006.[6] On September 6 of that year, an SGI press release heralded the end of the MIPS/IRIX product line.[7] Production ended on December 29, 2006, with last deliveries in March 2007, except by special arrangement. Support for these products ended in December 2013 and they will receive no further updates.[8]

Due to the bankruptcy of Silicon Graphics and its subsequent purchase by Rackable Systems, all current 'SGI' hardware is X86-64 based, incapable of running MIPS code, and shipped with Red Hat Enterprise Linux or SUSE Linux Enterprise Server.


IRIX 6 was compliant with UNIX System V Release 4, UNIX 95 and POSIX (including 1e/2c draft 15 ACLs and Capabilities).[9]

IRIX had strong support for real-time disk and graphics I/O. IRIX was one of the first Unix versions to feature a graphical user interface for the main desktop environment. IRIX was widely used in the computer animation industry and for scientific visualization due to its once-large application base.

IRIX was a leader in Symmetric Multi-Processing (SMP), scalable from 1 to greater than 1024 processors with a single system image.

IRIX used the Indigo Magic Desktop, which by default used the 4Dwm X window manager with a custom look designed using the Motif widget toolkit.

IRIX used the MIPSPro 7.4 Compiler for both its front end and back end. The compiler was designed to support parallel POSIX programming in C/C++, Fortran 77/90, and Ada. The Workshop GUI IDE was used for development. Other tools include Speedshop for performance tuning, and Performance Co-Pilot.[10]

IRIX also supported OpenGL for graphics chips and Image processing libraries.

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