PA-RISC information - since 1999

About OpenPA

OpenPA is an open information resource for HP PA-RISC based computers and technical architecture, a registered serial publication with ISSN 1866-2757. This site is a non-commercial resource for information on these systems and technical details. First published in 1999, OpenPA has been regularly updated for over two decades.

PA-RISC is a RISC computer architecture designed by Hewlett-Packard in the 1980s and used in a range of HP 9000 and Visualize workstations and servers between the 1980s and 2000s. Some PA-RISC predecessors of the 1980s as well as some successors based on the HP/Intel Itanium architecture of the 2000s are also covered.

OpenPA is based on public information from primary sources such as HP guides and handbooks as well as secondary articles, journals and conferences, published since the 1980s. Availability of information is rather dim these days as sources and repositories just disappeared.

Paul Weissmann is the editor of OpenPA and also publishes OpenKRITIS, a platform for operators of critical infrastructure. He can be reached via email.

An OpenPA Book Edition of the complete project is available with 358 pages.

How come? was founded in December 1999 at a time when Google just started and Wikipedia did not exist yet. The idea was a central independent resource for information on PA-RISC Unix computers, widely available in the second-hand market of the late 1990s and early 2000s. OpenPA development and contributions peaked in those early years with a lively community around PA-RISC and open source systems.


This site was started in 1999 when second-hand PA-RISC systems became affordable to hobbyists after being phased out in the industry for modern COTS Windows NT or Linux servers. Not much PA-RISC information was readily available on the web when other popular Unix and RISC platforms were documented rather well.

An 715/100 from a local newspaper ad started the interest and slowly led to an archive of PA-RISC documentation from the 90s available on the web — much of it from Mach and MkLinux projects. Edited into a simple web site with frames, it was published with hosting provided by Bill Bradford of SunHELP. The late Mickey appeared soon after, with lots of PA-RISC wisdom.

After two years, in 2001, the site was renamed and moved to its own Digital DECstation 5000 on 1Mb dialup. The increasing support from HP for the PA-RISC Linux project made a lot of official PA-RISC documentation available, with open source operating systems making significant progress, including versions of OpenBSD and Linux. Most of the HP 9000/700 and many of the lettered workstations were documented on OpenPA during that time, as were PA-RISC processors, chipsets and operating systems.


Updates became less frequent after 2005 with minor additions such as the PA-8800 and PA-8900 processors, PA-RISC architecture and operating systems. An OpenPA print edition was finally released with several hundred pages as PDF.

OpenPA in 2006

A spike of activity in 2008 resulted in much new content like the 64-bit PA-RISC workstations and rp Series servers, mainframes such as Convex SPP, V-Class and some early HP Itanium. Information on the fringes of PA-RISC was added, including third-party processors and OEM systems from Japan and early-1980s PA-RISC computers.


Update frequency and additions stalled considerably after 2008 with mostly low-intensity maintenance and reshuffling of content during more than a decade. The Internet and PA-RISC information changed a lot during that time.

OpenPA in 2012

Much of the original HP documentation disappeared during the 2010s so many links to original sources and references had to be removed. Interest in and support for PA-RISC in open-source systems dwindled as well.

Major housecleaning was done several times from 2016 on, checking links, content and rewriting much original language. Some new additions included the PA-RISC timeline and original equipment prices, a new OpenPA print edition and some restructured sections plus various cleanups in the backend.


OpenPA was refreshed again in the 2020s and some large new articles were written after the 20-year anniversary. An effort was made to find new sources and properly document PA-RISC history again.

OpenPA in 2021

Some new activities were started around the turn of the decade – content was made more readable, sources consolidated and some more unknown aspects of PA-RISC were documented, like PRO, the 1980s, HP-UX and weird operating systems, Apollo and PRISM and the Internet period in general.

Many OpenPA articles have been updated and streamlined during that time, bad ideas from previous years (decades) reversed and some severely outdated text rewritten with new language added to make everything more readable. There is still some old, original content scattered throughout OpenPA and many ideas still to be implemented, some of which were have been approached step by step.

The yearbook

Year Changes Content Backend
1999 Started PA-RISC overview from the 90s Frames, dark-mode
2000 7 HP 9000 700s, operating systems Hosted at sunhelp
2001 7 32-bit processors, hardware, more systems mickey@ appeared
2002 21 BSD, A/B/C/J lettered-systems, some 64-bit, X-Terms Renamed, own server
2003 30 Complete 64-bit, four-digit systems, 3rd-party, more OS
2004 14 Benchmarks, FOCUS, graphics, SCSI, architecture Complete revamp, CSS
2005 3 Small updates
2006 4 Final PA-RISCs - Mako, C8000 OpenPA book
2007 3 History, small updates Limited paperback
2008 18 Mainframe/Cell, Itanium, 1980s PA-RISC, others
2009 3 CPU and I/O architecture, much cleanup 10y anniversary
2010 2 T-Class, chipsets
2012 1 OpenPA book update
2014 1 Cleanup and housekeeping
2015 2 Handle disappearing sources and documents
2016 6 Restructure chipset content, timeline, cleanup
2018 3 PA-RISC story, OS updates, disappearing sources Cloud move
2019 20y anniversary
2020 3 Agilent PA-RISC, many systems updates
2021 2 Content mopup, OS history Backend mopup
2022 3 Research OS reorganization, Apollo/PRISM, mopup OpenPA book update
2023 5 PA-RISC history, 1980s, PRO in Japan, OpenPA and Internet
2024 5 Oddball OSs, HP-RT, HP-UX versions, Systems cleanup Frontend mopup

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Paul Weissmann is the maintainer and author of OpenPA since 1999. Many people helped OpenPA with contributions and support over the years, heartfelt thanks go to:

Thank you all!

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The copyright of the content on the pages belongs to Paul Weissmann, Berlin, Bonn, Palo Alto, San Francisco, unless otherwise noted. This site © 1999-2024 Paul Weissmann. No parts of this site may be reproduced or copied without prior written permission. Commercial use of the content is prohibited.

This site does not represent the Hewlett Packard company in any way. This site is not affiliated with Hewlett Packard in any way. It is provided as an informational resource only, for owners and users of PA-RISC computer systems and software and compatible systems. See also Legal Notes.

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