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{{short description|Variant of the Unix operating system developed by the Open Software Foundation}}
{{Infobox OS
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| developer              = [[Open Software Foundation]]<!-- Name of main developer or sponsor-->
| family                 = [[Unix]]<!-- "Unix-like" or "Microsoft Windows" -->
| working state          = Discontinued<!-- "Current", "Discontinued" (operating systems), or "No longer supported" (releases) -->
| source model           = <!-- "Open source", "Closed source", or "Shared source" -->
| released               = {{Start date and age|1992|1}}
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| supported platforms    = [[MIPS architecture|MIPS]], [[DEC Alpha]], [[PA-RISC]]<!-- IA-32, x64, Itanium, ARM, etc. -->
| kernel type            = Hybrid,<ref name="dtj1993winter_chang"/> [[Microkernel]]<ref name="byte199401_kernels"/><!-- Hybrid, Monolithic, Microkernel, Exokernel, Nanokernel, etc. -->
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'''OSF/1''' is a variant of the [[Unix]] [[operating system]] developed by the [[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]] developed at [[Carnegie Mellon University]], and is probably best known as the native Unix operating system for [[DEC Alpha]] architecture systems.

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

== Background ==
In 1988, during the so-called "[[Unix wars]]", [[Digital Equipment Corporation]] (DEC) joined with [[IBM]], [[Hewlett-Packard]], and others to form the [[Open Software Foundation]] (OSF) to develop a version of Unix named OSF/1. The aim was to compete with [[UNIX System V#SVR4|System V Release 4]] from [[AT&T Corporation]] and [[Sun Microsystems]], and it has been argued that a primary goal was for the operating system to be free of AT&T [[intellectual property]].<ref>{{cite book |author=Salus, Peter H. |title=A Quarter Century of UNIX |publisher=Addison-Wesley Pub. Co |location=Reading, Mass |year=1994 |page=217 |isbn=0-201-54777-5}}</ref> 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 | date=January 2024 | reason=A fact supported by a citation, but where is the citation?!}} Digital also strongly promoted OSF/1 for [[real-time computing|real-time]] applications, and with traditional UNIX implementations at the time providing poor real-time support at best, the real-time and [[thread (computing)|multi-threading]] 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 [[UNIX System V|System V]] and BSD.

OSF/1 at its inception combined Mach 2.5 with a large part of the [[Berkeley Software Distribution|BSD]] kernel (based on the 4.3-Reno release) to implement the UNIX [[API]],<ref name="usenix1993winter_zajcew">{{ cite journal | url=https://archive.org/details/1993-proceedings-winter-san-diego/page/449/mode/1up | title=An OSF/1 UNIX for Massively Parallel Multicomputers | journal=Proceedings of the Winter 1993 USENIX Conference | publisher=USENIX Association | date=1993 | access-date=23 January 2024 | first1=Roman | last1=Zajcew | first2=Paul | last2=Roy | first3=David | last3=Black | first4=Chris | last4=Peak | first5=Paulo | last5=Guedes | first6=Bradford | last6=Kemp | first7=John | last7=LoVerso | first8=Michael | last8=Leibensperger | first9=Michael | last9=Barnett | first10=Faramarz | last10=Rabii | first11=Durriya | last11=Netterwala | pages=449–468 }}</ref>{{rp | pages=451 | quote=OSF/1 is based on the Mach 2.5 operating system from Carnegie Mellon University. Both are integrated or monolithic kernel systems that implement the majority of system functionality in the operating system kernel (but not all, for example OSF/1’s program loader runs in user space). Their kernels contain the core Mach technology and additional Unix functionality. OSF/1 has significantly upgraded the 4.3BSD portion of Mach 2.5 to implement advanced features and obtain compliance with standards.}} with this monolithic kernel arrangement continuing through the OSF/1 1.2 release, although the adoption of a microkernel had already been foreseen.<ref name="osf1993_design">{{ cite book | url=https://archive.org/details/bitsavers_osfDesignostemRelease1.21990_25637674/page/n36/mode/1up | title=Design of the OSF/1 Operating System Release 1.2 | publisher=P T R Prentice-Hall Inc. | date=1993 | access-date=24 January 2024 | pages=1–12 | quote=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. }}</ref> 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.<ref name="byte199401_kernels">{{ cite magazine | url=https://archive.org/details/eu_BYTE-1994-01_OCR/page/n153/mode/1up | title=Small Kernels Hit It Big | magazine=Byte | last1=Varhol | first1=Peter D. | date=January 1994 | access-date=24 January 2024 | pages=119–120, 122, 124, 126, 128 }}</ref>

== Vendor releases ==
DEC's first release of OSF/1 (OSF/1 Release 1.0) in January 1992 was for its line of [[MIPS architecture|MIPS]]-based [[DECstation]] workstations,<ref>{{cite newsgroup | title = Press Release&nbsp;— OSF/1 | author = Ellen Minter | date = 1992-01-28 | newsgroup = bit.listserv.esl-l | message-id = 9201282310.AA15415@enet-gw.pa.dec.com | url = http://groups.google.com/group/bit.listserv.esl-l/msg/b099f187095ca972?dmode=source&hl=en | access-date = 2007-08-21 | archive-date = 2012-11-02 | archive-url = https://web.archive.org/web/20121102123154/http://groups.google.com/group/bit.listserv.esl-l/msg/b099f187095ca972?dmode=source&hl=en | url-status = live }}</ref> however this was never a fully supported product. DEC ported OSF/1 to their new [[DEC Alpha|Alpha AXP]] platform as DEC OSF/1 AXP Release 1.2, released in March 1993. OSF/1 AXP is a full [[64-bit]] operating system, preserving the kernel architecture based on Mach 2.5 and 4.3BSD components.<ref name="dtj1993winter_chang">{{ cite journal | url=https://archive.org/details/bitsavers_decdtjdtjv_9453190/page/n45/mode/2up | title=High-performance TCP/IP and UDP/IP Networking in DEC OSF/1 for Alpha AXP | journal=Digital Technical Journal | publisher=Digital Equipment Corporation | volume=5 | issue=1 | date=Winter 1993 | access-date=24 January 2024 | first1=Chran-Ham | last1=Chang | first2=Richard | last2=Flower | first3=John | last3=Forecast | first4=Heather | last4=Gray | first5=William R. | last5=Haive | first6=K. K. | last6=Ramakrishnan | first7=Ashok P. | last7=Nadkami | first8=Uttam N. | last8=Shikarpur | first9=Kathleen M. | last9=Wilde | pages=44–61 | quote=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. }}</ref> From OSF/1 AXP 2.0 onwards, [[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.<ref name="chang1996">{{ cite tech report | url=https://archive.org/details/nasa_techdoc_19960034349/page/n25/mode/1up | title=UNIX-Based Operating Systems Robustness Evaluation | last1=Chang | first1=Yu-Ming | publisher=University of Illinois at Urbana-Champaign | date=1996 | access-date=26 January 2024 | pages=10 }}</ref> Although OSF/1 2.0 was also developed for DECStation MIPS systems, it was "never officially released or sold".<ref name="dec_osf1_2.0_readme">{{ cite web | url=https://web-docs.gsi.de/~kraemer/COLLECTION/OSF1/X20-8/readme | title=DEC OSF/1 X2.0-8 (Rev. 155) for MIPS | author=Digital Equipment Corporation | date=July 1992 | access-date=22 June 2024 }}</ref> Subsequent releases are named Digital UNIX, and later, [[Tru64 UNIX]].

Upon its acquisition of [[Apollo Computer]] in 1989, [[Hewlett-Packard|HP]] announced plans to introduce OSF/1 on both companies' products by late 1990.<ref name="hpprofessional198907_apollo">{{ cite magazine | url=https://archive.org/details/HP-Professional_Vol._03_No._07_Jul_1989/page/16/mode/1up | title=HP Announces Plans For Apollo Division | magazine=HP Professional | date=July 1989 | access-date=15 April 2024 | volume=3 | issue=7 | pages=16 }}</ref> HP released a port of OSF/1 to the early [[HP 9000]]/700 workstations based on the [[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]].<ref name=openpa>{{cite web|title=OSF/1 on PA-RISC|url=https://www.openpa.net/osf_1_mkpa_pa-risc.html|work=OpenPA.net|access-date=29 December 2022|archive-date=23 July 2011|archive-url=https://web.archive.org/web/20110723233438/http://openpa.net/other.html#hp_osf1|url-status=live}}</ref>

As part of the [[AIM alliance]] and the resulting [[PowerOpen]] specification, [[Apple Inc.|Apple Computer]] intended to base [[A/UX]] 4.0 for its [[PowerPC]]-based [[Mac (computer)|Macintosh]]es upon OSF/1,<ref>{{cite news |first=Cate |last=Corcoran |date=4 November 1991 |title=Apple reveals plans for updated A/UX, PowerOpen Unix development alliance |newspaper=InfoWorld |url=https://books.google.com/books?id=Xz0EAAAAMBAJ&pg=PA1 |pages=1, 115 |access-date=11 February 2019 |archive-date=26 July 2020 |archive-url=https://web.archive.org/web/20200726125525/https://books.google.com/books?id=Xz0EAAAAMBAJ&pg=PA1 |url-status=live }}</ref> but the project was cancelled and PowerOpen deprecated.

IBM used OSF/1 as the basis of the [[IBM AIX#IBM mainframes|AIX/ESA]] operating system for [[IBM System/370|System/370]] and [[IBM System/390|System/390]] mainframes.<ref>{{cite web |url=http://www.findarticles.com/p/articles/mi_m0NEW/is_1992_April_1/ai_12162157 |archive-url=https://web.archive.org/web/20060224133234/http://www.findarticles.com/p/articles/mi_m0NEW/is_1992_April_1/ai_12162157 |archive-date=2006-02-24 |title=IBM announces AIX/ESA mainframe version of Unix |access-date=2008-03-28 | date=1992-04-01 }}</ref>

[[Intel Paragon]] supercomputers used a version of OSF/1 featuring the Mach 3.0 kernel.<ref name="intelparagon199310">{{ cite book | url=https://archive.org/details/bitsavers_intelsupergonXPSXPEBrochureOct93_4860969/page/n3/mode/1up | title=Intel Paragon Supercomputers | publisher=Intel Corporation | date=October 1993 | access-date=26 January 2024 | pages=4 }}</ref>

OSF/1 was also ported by [[Kendall Square Research]] to its proprietary [[microarchitecture]] used in the KSR1 [[supercomputer]].

== OSF MK ==
The Open Software Foundation created OSF MK, an evolution of OSF/1, incorporating the OSF Mach kernel (or OSF Microkernel<ref name="wells1996">{{ cite journal | url=https://archive.org/details/proceedingsofwor0000work_y7j9/page/186/mode/2up | title=Using Object Frameworks to Enable Real-Time and Dependability in a Modular Operating System | journal=Proceedings of WORDS'96 The Second Workshop on Object-Oriented Real-Time Dependable Systems | last1=Wells | first1=Douglas M. | date=February 1996 | access-date=24 January 2024 | pages=186–190 }}</ref>) 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.<ref name="wells1994" /> 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.<ref name="morin1997">{{ cite book | url=https://archive.org/details/mklinux00rich/page/143/mode/1up | title=MkLinux: Microkernel Linux for the Power Macintosh | publisher=Prime Time Freeware | date=1998 | access-date=24 January 2024 | isbn=1-881957-24-1 | last1=Morin | first1=Rich | pages=143 }}</ref> In OSF MK, it contains applicable code from the [[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]] Mach 3.0 kernel.<ref>Archived at [https://ghostarchive.org/varchive/youtube/20211212/ggnFoDqzGMU Ghostarchive]{{cbignore}} and the [https://web.archive.org/web/20181031185303/https://www.youtube.com/watch?v=ggnFoDqzGMU&gl=US&hl=en Wayback Machine]{{cbignore}}: {{cite AV media|url=https://www.youtube.com/watch?v=ggnFoDqzGMU|author=Jim Magee|title=WWDC 2000 Session 106 – Mac OS X: Kernel|minutes=12}}{{cbignore}}</ref><ref>{{cite web| url = http://www.db.opengroup.org/ar/technologies/mk-dbleplus/white_paper.htm| archive-url = https://web.archive.org/web/20170822055033/http://www.db.opengroup.org/ar/technologies/mk-dbleplus/white_paper.htm| archive-date = 2017-08-22 |url-status=dead| title = MK++: A High Performance, High Assurance Microkernel}}</ref> It also consists of improvements made by the OSF such as built-in collocation capability, realtime improvements, and rewriting of the [[Inter-process communication|IPC]] [[remote procedure call|RPC]] component for better performance.<ref name="wells1994">{{cite conference |url=https://pdfs.semanticscholar.org/03ac/1296f530719497b49d7580b55a2d9b8353ab.pdf|archive-url=https://web.archive.org/web/20170822053715/https://pdfs.semanticscholar.org/03ac/1296f530719497b49d7580b55a2d9b8353ab.pdf|archive-date=2017-08-22|url-status=dead|title=A Trusted, Scalable, Real-Time Operating System Environment |conference=1994 IEEE Dual-Use Technologies and Applications Conference |author=Douglas M. Wells|year=1994 |s2cid=5205380}}</ref>

== OSF/1 AD ==
OSF/1 AD (''Advanced Development'') was a [[distributed operating system|distributed]] version of OSF/1 developed for [[massively parallel]] supercomputers by [[Locus Computing Corporation]].<ref name="zajcew">{{cite conference|title=An OSF/1 UNIX for Massively Parallel Multicomputers |url=ftp://ribot1.ac.upc.es/pub/archives/gso/mach.OSF/os_coll_papers/osf1ad_usenix.ps |format=PostScript |last=Zajcew |first=Roman |conference=USENIX Winter 1993 Technical Conference |conference-url=http://www.usenix.org/publications/library/proceedings/sd93/ |year=1993 |display-authors=etal }}{{dead link|date=May 2017 |bot=InternetArchiveBot |fix-attempted=yes }}</ref> Variants of OSF/1 AD are on several such systems, including the [[Intel Paragon]] XP/S and [[ASCI Red]], [[Convex Computer|Convex]] Exemplar SPP-1200 (as ''SPP-UX'') and the [[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]].<ref name="computerworld19900514_mach">{{ cite magazine | url=https://archive.org/details/computerworld2420unse/page/97/mode/1up | title=Move over, Unix: Here comes Mach! | magazine=Computerworld | last1=Anthes | first1=Gary H. | date=14 May 1990 | access-date=15 April 2024 | pages=97–98 }}</ref> 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.<ref name="ida199711_p3375">{{ cite tech report | url=https://archive.org/details/DTIC_ADA349992/page/66/mode/2up | title=Assessing DoD Goal Security Architecture (DGSA) Support in Commercially Available Operating Systems and Hardware Platforms | publisher=Institute for Defense Analyses | date=November 1997 | access-date=15 April 2024 | last1=Schneider | first1=Edward A. | last2=Feustel | first2=Edward A. | last3=Ross | first3=Ronald S. | pages=66-67 }}</ref> 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.<ref name="hpprofessional198907_apollo"/>

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,<ref name="unigramx19900514_osf">{{ cite news | url=https://archive.org/details/UnigramX1990263-313/page/n128/mode/1up | title=OSF Solidifies Plans to Purge AT&T Code | work=Unigram/X | date=14 May 1990 | access-date=25 July 2024 | pages=1 }}</ref> leading to speculation that a system based on the [[Chorus Systèmes SA|Chorus]] microkernel might supplant Mach entirely and become OSF/2 itself.<ref name="unigramx19910903_osf">{{ cite news | url=https://archive.org/details/UnigramX1990263-313/page/n230/mode/1up | title=Micro-Kernel, Real-Time Chorus is "Future of Unix" AT&T and Open Software Foundation Talks in Progress | work=Unigram/X | date=3 September 1990 | access-date=25 July 2024 | pages=1 }}</ref> 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.<ref name="unigramx19910527_osf">{{ cite news | url=https://archive.org/details/UnigramX1991314-365/page/n131/mode/1up | title=AT&T code-free Mach 3.0 is now shipping to computer vendors | work=Unigram/X | last1=O'Gara | first1=Maureen | date=27 May 1991 | access-date=25 July 2024 | pages=2 }}</ref>

== References ==
{{Reflist}}

{{Mach-like}}
{{unix-like}}

[[Category:Discontinued operating systems]]
[[Category:Mach (kernel)]]
[[Category:Microkernel-based operating systems]]
[[Category:Unix variants]]
[[Category:Computer-related introductions in 1992]]