# OSF/1

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**OSF/1** is a variant of the [Unix](/source/Unix) [operating system](/source/Operating_system) developed by the [Open Software Foundation](/source/Open_Software_Foundation) during the late 1980s and early 1990s. OSF/1 is one of the first operating systems to have used the [Mach kernel](/source/Mach_kernel) developed at [Carnegie Mellon University](/source/Carnegie_Mellon_University), and is probably best known as the native Unix operating system for [DEC Alpha](/source/DEC_Alpha) architecture systems.

In 1994, after AT&T had sold [UNIX System V](/source/UNIX_System_V) to [Novell](/source/Novell) and the rival [Unix International](/source/Unix_International) consortium had disbanded, the Open Software Foundation ceased funding of research and development of OSF/1. The [Tru64 UNIX](/source/Tru64_UNIX) variant of OSF/1 was supported by [HP](/source/Hewlett-Packard) until 2012.

## Background

In 1988, during the so-called "[Unix wars](/source/Unix_wars)", [Digital Equipment Corporation](/source/Digital_Equipment_Corporation) (DEC) joined with [IBM](/source/IBM), [Hewlett-Packard](/source/Hewlett-Packard), and others to form the [Open Software Foundation](/source/Open_Software_Foundation) (OSF) to develop a version of Unix named OSF/1. The aim was to compete with [System V Release 4](/source/UNIX_System_V#SVR4) from [AT&T Corporation](/source/AT%26T_Corporation) and [Sun Microsystems](/source/Sun_Microsystems), and it has been argued that a primary goal was for the operating system to be free of AT&T [intellectual property](/source/Intellectual_property).[3] The fact that OSF/1 is one of the first operating systems to have used the Mach kernel is cited as support of this assertion.[citation needed] Digital also strongly promoted OSF/1 for [real-time](/source/Real-time_computing) applications, and with traditional UNIX implementations at the time providing poor real-time support at best, the real-time and [multi-threading](/source/Thread_(computing)) support can be interpreted as having been heavily dependent on the Mach kernel. At the time of its introduction, OSF/1 became the third major flavor of UNIX together with [System V](/source/UNIX_System_V) and BSD.

OSF/1 at its inception combined Mach 2.5 with a large part of the [BSD](/source/Berkeley_Software_Distribution) kernel (based on the 4.3-Reno release) to implement the UNIX [API](/source/API),[4]: 451 with this monolithic kernel arrangement continuing through the OSF/1 1.2 release, although the adoption of a microkernel had already been foreseen.[5] OSF/1 1.3 introduced such a microkernel in the form of Mach 3.0, hosting Unix system services separately in user space to provide the existing OSF/1 functionality.[2]

## Vendor releases

DEC's first release of OSF/1 (OSF/1 Release 1.0) in January 1992 was for its line of [MIPS](/source/MIPS_architecture)-based [DECstation](/source/DECstation) workstations,[6] however this was never a fully supported product. DEC ported OSF/1 to their new [Alpha AXP](/source/DEC_Alpha) platform as DEC OSF/1 AXP Release 1.2, released in March 1993. OSF/1 AXP is a full [64-bit](/source/64-bit) operating system, preserving the kernel architecture based on Mach 2.5 and 4.3BSD components.[1] From OSF/1 AXP 2.0 onwards, [UNIX System V](/source/UNIX_System_V) compatibility was also integrated into the system, but the architecture remained centred on the Mach 2.5 modular kernel, unlike later OSF versions of the system.[7] Although OSF/1 2.0 was also developed for DECStation MIPS systems, it was "never officially released or sold".[8] Subsequent releases are named Digital UNIX, and later, [Tru64 UNIX](/source/Tru64_UNIX).

Upon its acquisition of [Apollo Computer](/source/Apollo_Computer) in 1989, [HP](/source/Hewlett-Packard) announced plans to introduce OSF/1 on both companies' products by late 1990.[9] HP released a port of OSF/1 to the early [HP 9000](/source/HP_9000)/700 workstations based on the [PA-RISC](/source/PA-RISC) 1.1 architecture. This was withdrawn soon afterwards due to lack of software and hardware support compared to competing operating systems, specifically [HP-UX](/source/HP-UX).[10]

As part of the [AIM alliance](/source/AIM_alliance) and the resulting [PowerOpen](/source/PowerOpen) specification, [Apple Computer](/source/Apple_Inc.) intended to base [A/UX](/source/A/UX) 4.0 for its [PowerPC](/source/PowerPC)-based [Macintoshes](/source/Mac_(computer)) upon OSF/1,[11] but the project was cancelled and PowerOpen deprecated.

IBM used OSF/1 as the basis of the [AIX/ESA](/source/IBM_AIX#IBM_mainframes) operating system for [System/370](/source/IBM_System/370) and [System/390](/source/IBM_System/390) mainframes.[12]

[Intel Paragon](/source/Intel_Paragon) supercomputers used a version of OSF/1 featuring the Mach 3.0 kernel.[13]

OSF/1 was also ported by [Kendall Square Research](/source/Kendall_Square_Research) to its proprietary [microarchitecture](/source/Microarchitecture) used in the KSR1 [supercomputer](/source/Supercomputer).

## OSF MK

The Open Software Foundation created OSF MK, an evolution of OSF/1, incorporating the OSF Mach kernel (or OSF Microkernel[14]) based on Mach 3.0 along with a variety of other functionality including the OSF/1 Single Server providing the Unix system personality. The complete system in the form of MK 5.0 was made available under commercial terms to OSF/1 licensees in April 1993.[15] In contrast to the OSF/1 server, which was encumbered by proprietary Unix licensing, the microkernel itself remained freely available for adoption by other projects.[16] In OSF MK, it contains applicable code from the [University of Utah](/source/University_of_Utah) Mach 4 kernel (such as the "Shuttles" modification used to speed up message passing) and applicable code from the many Mach 3.0 variants that sprouted off from the original [Carnegie Mellon University](/source/Carnegie_Mellon_University) Mach 3.0 kernel.[17][18] It also consists of improvements made by the OSF such as built-in collocation capability, realtime improvements, and rewriting of the [IPC](/source/Inter-process_communication) [RPC](/source/Remote_procedure_call) component for better performance.[15]

## OSF/1 AD

OSF/1 AD (*Advanced Development*) was a [distributed](/source/Distributed_operating_system) version of OSF/1 developed for [massively parallel](/source/Massively_parallel) supercomputers by [Locus Computing Corporation](/source/Locus_Computing_Corporation).[19] Variants of OSF/1 AD are on several such systems, including the [Intel Paragon](/source/Intel_Paragon) XP/S and [ASCI Red](/source/ASCI_Red), [Convex](/source/Convex_Computer) Exemplar SPP-1200 (as *SPP-UX*) and the [Hitachi](/source/Hitachi) SR2201 (as *HI-UX MPP*).

## OSF/2

OSF/2, a successor to OSF/1, was described as being based on the TMach system developed by [Trusted Information Systems](/source/Trusted_Information_Systems).[20] TMach, or Trusted Mach, was an operating system architecture incorporating the OSF Mach MK++ kernel, introducing a trusted computing base layer consisting of trusted server components, hosting an application layer in which untrusted programs would run.[21] In 1989, HP announced plans to merge the software platforms of its own products and those of newly acquired Apollo Computer to form a single OSF/2-compliant platform to be delivered by 1992.[9]

Other interpretations of the OSF/2 name were associated with various plans to remove AT&T-licensed code from early forms of OSF/1 and the Mach kernel in particular,[22] leading to speculation that a system based on the [Chorus](/source/Chorus_Syst%C3%A8mes_SA) microkernel might supplant Mach entirely and become OSF/2 itself.[23] With such a Chorus-based architecture having been rejected in favour of the Mach 3.0 microkernel, the OSF/2 designation persisted in reporting of this particular form of OSF/1.[24]

## References

1. Chang, Chran-Ham; Flower, Richard; Forecast, John; Gray, Heather; Haive, William R.; Ramakrishnan, K. K.; Nadkami, Ashok P.; Shikarpur, Uttam N.; Wilde, Kathleen M. (Winter 1993). ["High-performance TCP/IP and UDP/IP Networking in DEC OSF/1 for Alpha AXP"](https://archive.org/details/bitsavers_decdtjdtjv_9453190/page/n45/mode/2up). *Digital Technical Journal*. **5** (1): 44–61. Digital Equipment Corporation. Retrieved 24 January 2024. DEC OSF/1 operating system version 1.2 for Alpha AXP systems is an implementation of the Open Software Foundation (OSF) OSF/1 version 1.0 and version 1.1 technology. The operating system is a 64-bit kernel architecture based on Carnegie-Mellon University's Mach version 2.5 kernel. Components from 4.3 BSD are included, in addition to UNIX System Laboratories System V interface compatibility.

1. Varhol, Peter D. (January 1994). ["Small Kernels Hit It Big"](https://archive.org/details/eu_BYTE-1994-01_OCR/page/n153/mode/1up). *Byte*. pp. 119–120, 122, 124, 126, 128. Retrieved 24 January 2024.

1. Salus, Peter H. (1994). *A Quarter Century of UNIX*. Reading, Mass: Addison-Wesley Pub. Co. p. 217. ISBN 0-201-54777-5.

1. Zajcew, Roman; Roy, Paul; Black, David; Peak, Chris; Guedes, Paulo; Kemp, Bradford; LoVerso, John; Leibensperger, Michael; Barnett, Michael; Rabii, Faramarz; Netterwala, Durriya (1993). ["An OSF/1 UNIX for Massively Parallel Multicomputers"](https://archive.org/details/1993-proceedings-winter-san-diego/page/449/mode/1up). *Proceedings of the Winter 1993 USENIX Conference*. USENIX Association. Retrieved 23 January 2024.

1. [*Design of the OSF/1 Operating System Release 1.2*](https://archive.org/details/bitsavers_osfDesignostemRelease1.21990_25637674/page/n36/mode/1up). P T R Prentice-Hall Inc. 1993. pp. 1–12. Retrieved 24 January 2024. Currently, OSF/1 integrates the core kernel services with the system services into one monolithic kernel. In future versions, the kernel will contain only the primitive objects and operations provided by a microkernel; most of what is now contained in the system services will be moved into its own, separate address space.

1. Ellen Minter (1992-01-28). ["Press Release — OSF/1"](http://groups.google.com/group/bit.listserv.esl-l/msg/b099f187095ca972?dmode=source&hl=en). bit.listserv.esl-l. [Archived](https://web.archive.org/web/20121102123154/http://groups.google.com/group/bit.listserv.esl-l/msg/b099f187095ca972?dmode=source&hl=en) 2012-11-02 at the Wayback Machine. Retrieved 2007-08-21.

1. Chang, Yu-Ming (1996). [*UNIX-Based Operating Systems Robustness Evaluation*](https://archive.org/details/nasa_techdoc_19960034349/page/n25/mode/1up). University of Illinois at Urbana-Champaign. p. 10. Retrieved 26 January 2024.

1. Digital Equipment Corporation (July 1992). ["DEC OSF/1 X2.0-8 (Rev. 155) for MIPS"](https://web-docs.gsi.de/~kraemer/COLLECTION/OSF1/X20-8/readme). Retrieved 22 June 2024.

1. ["HP Announces Plans For Apollo Division"](https://archive.org/details/HP-Professional_Vol._03_No._07_Jul_1989/page/16/mode/1up). *HP Professional*. Vol. 3, no. 7. July 1989. p. 16. Retrieved 15 April 2024.

1. ["OSF/1 on PA-RISC"](https://www.openpa.net/osf_1_mkpa_pa-risc.html). *OpenPA.net*. [Archived](https://web.archive.org/web/20110723233438/http://openpa.net/other.html#hp_osf1) 23 July 2011 at the Wayback Machine. Retrieved 29 December 2022.

1. Corcoran, Cate (4 November 1991). ["Apple reveals plans for updated A/UX, PowerOpen Unix development alliance"](https://books.google.com/books?id=Xz0EAAAAMBAJ&pg=PA1). *InfoWorld*. pp. 1, 115. [Archived](https://web.archive.org/web/20200726125525/https://books.google.com/books?id=Xz0EAAAAMBAJ&pg=PA1) 26 July 2020 at the Wayback Machine. Retrieved 11 February 2019.

1. ["IBM announces AIX/ESA mainframe version of Unix"](http://www.findarticles.com/p/articles/mi_m0NEW/is_1992_April_1/ai_12162157). 1992-04-01. [Archived](https://web.archive.org/web/20060224133234/http://www.findarticles.com/p/articles/mi_m0NEW/is_1992_April_1/ai_12162157) 2006-02-24 at the Wayback Machine. Retrieved 2008-03-28.

1. [*Intel Paragon Supercomputers*](https://archive.org/details/bitsavers_intelsupergonXPSXPEBrochureOct93_4860969/page/n3/mode/1up). Intel Corporation. October 1993. p. 4. Retrieved 26 January 2024.

1. Wells, Douglas M. (February 1996). ["Using object frameworks to enable real-time and dependability in a modular operating system"](https://archive.org/details/proceedingsofwor0000work_y7j9/page/186/mode/2up). *Proceedings of WORDS'96. The Second Workshop on Object-Oriented Real-Time Dependable Systems*. pp. 186–190. [doi:10.1109/WORDS.1996.506282](https://doi.org/10.1109/WORDS.1996.506282). ISBN 0-8186-7570-5. Retrieved 24 January 2024.

1. Douglas M. Wells (1994). [*A Trusted, Scalable, Real-Time Operating System Environment*](https://web.archive.org/web/20170822053715/https://pdfs.semanticscholar.org/03ac/1296f530719497b49d7580b55a2d9b8353ab.pdf). 1994 IEEE Dual-Use Technologies and Applications Conference. [S2CID 5205380](https://api.semanticscholar.org/CorpusID:5205380). Archived from [the original](https://pdfs.semanticscholar.org/03ac/1296f530719497b49d7580b55a2d9b8353ab.pdf) on 2017-08-22.

1. Morin, Rich (1998). [*MkLinux: Microkernel Linux for the Power Macintosh*](https://archive.org/details/mklinux00rich/page/143/mode/1up). Prime Time Freeware. p. 143. ISBN 1-881957-24-1. Retrieved 24 January 2024.

1. Archived at [Ghostarchive](https://ghostarchive.org/varchive/youtube/20211212/ggnFoDqzGMU) and the [Wayback Machine](https://web.archive.org/web/20181031185303/https://www.youtube.com/watch?v=ggnFoDqzGMU&gl=US&hl=en): Jim Magee. [*WWDC 2000 Session 106 – Mac OS X: Kernel*](https://www.youtube.com/watch?v=ggnFoDqzGMU). p. 12.

1. ["MK++: A High Performance, High Assurance Microkernel"](https://web.archive.org/web/20170822055033/http://www.db.opengroup.org/ar/technologies/mk-dbleplus/white_paper.htm). Archived from [the original](http://www.db.opengroup.org/ar/technologies/mk-dbleplus/white_paper.htm) on 2017-08-22.

1. Zajcew, Roman et al. (1993). [*An OSF/1 UNIX for Massively Parallel Multicomputers*](ftp://ribot1.ac.upc.es/pub/archives/gso/mach.OSF/os_coll_papers/osf1ad_usenix.ps) (PostScript). USENIX Winter 1993 Technical Conference.[dead link]

1. Anthes, Gary H. (14 May 1990). ["Move over, Unix: Here comes Mach!"](https://archive.org/details/computerworld2420unse/page/97/mode/1up). *Computerworld*. pp. 97–98. Retrieved 15 April 2024.

1. Schneider, Edward A.; Feustel, Edward A.; Ross, Ronald S. (November 1997). [*Assessing DoD Goal Security Architecture (DGSA) Support in Commercially Available Operating Systems and Hardware Platforms*](https://archive.org/details/DTIC_ADA349992/page/66/mode/2up). Institute for Defense Analyses. pp. 66–67. Retrieved 15 April 2024.

1. ["OSF Solidifies Plans to Purge AT&T Code"](https://archive.org/details/UnigramX1990263-313/page/n128/mode/1up). *Unigram/X*. 14 May 1990. p. 1. Retrieved 25 July 2024.

1. ["Micro-Kernel, Real-Time Chorus is "Future of Unix" AT&T and Open Software Foundation Talks in Progress"](https://archive.org/details/UnigramX1990263-313/page/n230/mode/1up). *Unigram/X*. 3 September 1990. p. 1. Retrieved 25 July 2024.

1. O'Gara, Maureen (27 May 1991). ["AT&T code-free Mach 3.0 is now shipping to computer vendors"](https://archive.org/details/UnigramX1991314-365/page/n131/mode/1up). *Unigram/X*. p. 2. Retrieved 25 July 2024.

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Adapted from the Wikipedia article [OSF/1](https://en.wikipedia.org/wiki/OSF%2F1) by Wikipedia contributors ([contributor history](https://en.wikipedia.org/wiki/OSF%2F1?action=history)). Available under [Creative Commons Attribution-ShareAlike 4.0 International](https://creativecommons.org/licenses/by-sa/4.0/). Changes may have been made.