Xenix under Bochs
|Company / developer||Microsoft, SCO, various resellers|
|Source model||Closed source|
|Latest release||System V release 2.3.4 / 1989|
|Supported platforms||PC/XT, x86, PDP-11, Z8001, 68k|
|Kernel type||Monolithic kernel|
|Succeeded by||SCO UNIX|
Xenix is a discontinued version of the Unix operating system for various microcomputer platforms, licensed by Microsoft from AT&T Corporation in the late 1970s. The Santa Cruz Operation (SCO) later acquired exclusive rights to the software, and eventually replaced it by SCO UNIX (now known as SCO OpenServer).
In the late 1980s Xenix was "probably the most widespread version of the UNIX operating system, according to the number of machines on which it runs", according to developers of the BSD version of Unix; Microsoft chairman Bill Gates said in 1996 that for a long time his firm had the highest-volume AT&T Unix license.
Bell Labs, Unix's developer, was part of the regulated Bell System and could not sell Unix. It instead licensed the software to others. Microsoft, which expected that Unix would be its operating system of the future when personal computers became powerful enough, purchased a license for Version 7 Unix from AT&T in 1978, and announced on August 25, 1980 that it would make it available for the 16-bit microcomputer market. Because Microsoft was not able to license the "UNIX" name itself, the company gave it an original name. Microsoft, in turn, did not sell Xenix directly to end users; instead, they licensed it to OEMs such as IBM, Intel, Tandy, Altos, SCO, and Siemens (SINIX) who then ported it to their own proprietary computer architectures.
Microsoft Xenix originally ran on the PDP-11. The first port was for the Zilog Z8001 16-bit processor: the first customer ship was January 1981 for Central Data Corporation of Illinois:4, followed in March 1981 by Paradyne Corporation's Z8001 product.:14 The first 8086 port was for the Altos Computer Systems' non-PC-compatible 8600-series computers (first customer ship date Q1 1982).[note 1]:3 Intel sold complete computers with Xenix under their Intel System 86 brand (with specific models such as 86/330 or 86/380X); they also offered the individual boards that made these computers under their iSBC brand. This included processor boards like iSBC 86/12 and also MMU boards such as the iSBC 309. The first Intel Xenix systems shipped in July 1982.:9[note 2] Tandy Corporation shipped TRS-XENIX for their 68000-based systems in January 1983. Seattle Computer Products also made (PC-incompatible) 8086 computers bundled with Xenix, like their Gazelle II, which used the S-100 bus and was available in late 1983 or early 1984.:17 There was also a port for IBM System 9000.
SCO had initially worked on their own PDP-11 port of V7, called Dynix,[note 3] but then struck an agreement with Microsoft for joint development and technology exchange on Xenix in 1982. In 1984, a port to the 68000-based Apple Lisa was jointly developed by SCO and Microsoft and it was the first shrink-wrapped binary product sold by SCO.
The difficulty in porting to the various 8086 and Z8000-based machines, said Microsoft in their 1983 OEM directory, had been the lack of a standardized memory management unit and protection facilities. Hardware manufacturers compensated by designing their own hardware, but the ensuing complexity made it "extremely difficult if not impossible for the very small manufacturer to develop a computer capable of supporting a system such as XENIX from scratch," and "the XENIX kernel must be custom-tailored to each new hardware environment.":Introduction A generally available port to the unmapped Intel 8086/8088 architecture was done by The Santa Cruz Operation around 1983. SCO Xenix for the PC XT shipped sometime in 1984 and contained some enhancement from 4.2BSD; it also supported the Micnet local area networking. The later 286 version of Xenix leveraged the integrated MMU present on this chip, by running in 286 protected mode. The 286 Xenix was accompanied by new hardware from Xenix OEMs. For example, the Sperry PC/IT, an IBM PC AT clone, was advertised as capable of supporting eight simultaneous dumb terminal users under this version.
While Xenix 2.0 was still based on Version 7 Unix, version 3.0 was upgraded to a Unix System III code base,:9 A 1984 Intel manual for Xenix 286 noted that the Xenix kernel had about 10,000 lines at this time.:1–7 It was followed by a System V.2 codebase in Xenix 5.0 (aka Xenix System V).
After the breakup of the Bell System AT&T started selling Unix. Microsoft, believing that it could not compete with Unix's developer, decided to abandon Xenix. The decision was not immediately transparent, and so Xenix gave birth to the term vaporware. An agreement was signed with IBM to develop OS/2, and the Xenix team (together with the best MS-DOS developers) was assigned to that project. In 1987 Microsoft transferred ownership of Xenix to SCO in an agreement that left Microsoft owning 25% of SCO. When Microsoft eventually lost interest in OS/2 as well, it based its further high-end strategy on Windows NT.
In 1987, SCO ported Xenix to the 386 processor, a 32-bit chip, this after securing knowledge from Microsoft insiders that Microsoft was no longer developing Xenix. Xenix System V release 2.3.1 introduced support for i386, SCSI and TCP/IP. SCO's Xenix System V/386 was the first 32-bit operating system available on the market for the x86 CPU Architecture.
Microsoft continued to use Xenix internally, submitting a patch to support functionality in UNIX to AT&T in 1987, which trickled down to the code base of both Xenix and SCO UNIX. Microsoft is said to have used Xenix on Sun workstations and VAX minicomputers extensively within their company as late as 1992. All internal Microsoft email transport was done on Xenix-based 68000 systems until 1995-96, when the company moved to its own Exchange Server product.
SCO released its SCO UNIX as a higher-end product, based on System V.3 and offering a number of technical advances over Xenix; Xenix remained in the product line. In the meantime, AT&T and Sun Microsystems completed the merge of Xenix, BSD, SunOS and System V.3 into System V Release 4. The last version of SCO Xenix/386 itself was System V.2.3.4, released in 1991.
Aside from its AT&T Unix base, Xenix incorporated elements from BSD, notably the vi text editor and its supporting libraries (termcap and curses). Its kernel featured some original extensions by Microsoft, notably file locking and semaphores,:1.12 while to the userland Microsoft added a "visual shell" for menu-driven operation instead of the traditional Unix shell. A limited form of local networking over serial lines (RS-232 ports) was possible through the "micnet" software, which supported file transfer and electronic mail, although UUCP was still used for networking via modems.
Trusted Xenix was a variant developed by Trusted Information Systems which incorporated the Bell-La Padula model of multilevel security, and had a multilevel secure interface for the STU-III secure communications device (that is, an STU-III connection would only be made available to applications running at the same privilege level as the key loaded in the STU-III). It was evaluated by formal methods and achieved a B2 security rating under the DoD's Trusted Computer System Evaluation Criteria—the second highest rating ever achieved by an evaluated operating system. Version 2.0 was released in January 1991, version 3.0 in April 1992, and version 4.0 in September 1993. It was still in use as late as 1995.
- Leffler, Samuel J.; Marshall Kirk McKusick, Michael J. Karels and John S. Quarterman (October 1989). The Design and Implementation of the 4.3BSD UNIX Operating System. Addison-Wesley. p. 7. ISBN 0-201-06196-1.
- "Unix Expo — Remarks by Bill Gates". 9 October 1996. Archived from the original on 18 August 2001. Retrieved 9 September 2013.
- Letwin, Gordon (1995-08-17). "What's happening to OS/2". comp.os.ms-windows.misc,comp.os.os2.advocacy. Web link. Retrieved 6 November 2013.
- Steve D. Pate (1996). Unix Internals: A Practical Approach. Addison Wesley Professional. p. 9. ISBN 978-0-201-87721-2. "Microsoft licensed Seventh Edition UNIX from AT&T in 1978 to produce the XENIX operating system initially for the PDP-11."
- "Xenix variant information". 2010-02-26. "In the late 1970s Microsoft licensed Unix source code from AT&T, which at the time was not licensing the name Unix."[dead link]
- P.A. Korn, J.P. McAdaragh and C.L. Tondo (1985). "Expanded personal computing power and capability". IBM Systems Journal 24 (1).
- Overview of the XENIX 286 Operating System. Intel Corporation. November 1984. "XENIX 286 is Intel's value-added version of the XENIX operating system released by Microsoft Corporation."
- Microsoft Xenix Operating System OEM Directory, May 1, 1983, Part No. OEM0091B
- Altos Unveils 16-Bit Micros With Unix, 1M-Byte Memory. Computerworld. 23 November 1981. pp. 49–50. ISSN 00104841.
- John Halamka (7 November 1983). Review: Altos 586. InfoWorld. p. 89. ISSN 01996649.
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- BYTE Guide to the IBM PC, fall 1984, p.61
- Steve D. Pate (1996). Unix Internals: A Practical Approach. Addison Wesley Professional. p. 9. ISBN 978-0-201-87721-2. ""The Santa Cruz Operation (SCO) was formed in 1979 by Larry and Doug Michels as a technical management consulting business. [...] SCO then changed its focus from consulting to the custom porting of UNIX system software and applications. The first version of UNIX which SCO developed and sold was called Dynix, a name subsequently used by Sequent. The operating system was based on Seventh Edition UNIX and ran on the PDP-11. [...] In 1982, a joint development and technology exchange agreement was reached between SCO and Microsoft bringing together engineers from SCO and Microsoft to further enhance the XENIX operating system which was increasing in popularity."
- Steve D. Pate (1996). Unix Internals: A Practical Approach. Addison Wesley Professional. p. 10. ISBN 978-0-201-87721-2. "In 1984 a port of XENIX was made to the Apple Lisa by SCO and Microsoft, and was subsequently sold successfully by SCO as their first binary product, showing the success of the shrink-wrapped market. A port was also made to the Tandy model 16B."
- Hare, John Bruno; Thomas Dean Thomas (1984). "Porting Xenix to the Unmapped 8086". Proceedings of the USENIX Winter Conference. Washington, D.C.: USENIX Association.
- "SCO Company History". Operating System Documentation Project. Retrieved 2008-05-14.
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- Steve D. Pate (1996). Unix Internals: A Practical Approach. Addison Wesley Professional. p. 10. ISBN 978-0-201-87721-2. "In 1983 the PC [XT] emerged. SCO started porting to the 8088 but concentrated on the 8086, producing a release of SCO XENIX in 1984 which ran in 640 Kbytes with a 10 Mbyte hard disk. The release could support three or more users simultaneously, had multiscreen (virtual console) facilities, Micnet local area networking and enhancements added from 4.2BSD."
- Microsoft Xenix 3.0 ready for 286
- SCO UNIX in a Nutshell. "O'Reilly Media, Inc.". 1994. pp. 312–. ISBN 978-1-56592-037-8.
- Æleen Frisch (2002). Essential System Administration: Tools and Techniques for Linux and Unix Administration. O'Reilly Media, Inc. p. xiii. ISBN 978-0-596-55049-3.
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- J. E. Lapin (1987). Portable C and Unix System Programming. Pearson Education. p. 106. ISBN 978-0-13-686494-3. "The XENIX 2.3 version generally resembles V7's [ABI]; the XENIX 3.0 version resembles SIII's, and the XENIX 5.0 version resembles SV2's."
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- Gligor, V.D.; Chandersekaran, C.S.; Chapman, R.S. (February 1987), "Design and Implementation of Secure Xenix", IEEE Transactions on Software Engineering, SE-13 (2): 208–221, ISSN 0098-5589
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- Kaare Christian (29 May 1984). "A UNIX to be Proud Of". PC Magazine: 165–172. ISSN 0888-8507.; review of the beta SCO Xenix on an XT
- William B. Twitty (1984). UNIX on the IBM PC. Prentice-Hall. ISBN 978-0-13-939075-3. Covers and compares PC/IX, Xenix and Venix.
- Robin Raskin; Kaare Christian (August 1986). "Xenix System V: A multiuser answer for the AT?". PC Magazine: 253–266. ISSN 0888-8507.
|Wikimedia Commons has media related to Xenix.|
- Photograph, requirements, and description of SCO Xenix 386 circa-1988 at the Wayback Machine (archived January 23, 2010)
- Xenix documentation and books for Download
- Xenix man pages
- Unsorted Xenix images, scans and photos
- Intel Multibus System 320 for Xenix (or iRMX86)
- Welcome to comp.unix.xenix.sco (v 1.64)
- A conversation with Doug Michels, co-founder of SCO on YouTube