PA-RISC information - since 1999

About OpenPA

OpenPA is an information resource for HP PA-RISC based computers and technical architecture, a registered serial publication with ISSN 1866-2757.

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 successors based on the HP/Intel Itanium architecture are also covered. This site is a non-commercial resource for information on these systems and technical details. First published in 1999, OpenPA is regularly updated with new or corrected content.

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

Since Summer 2006 an OpenPA Print Version monograph PDF version of the complete OpenPA project has been available for printing and off-line viewing.

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 hobbyist market of the late 1990s and early 2000s. OpenPA development and contributions peaked in those early years between 1999-2002 with a lively community around PA-RISC and open source systems. Most PA-RISC and HP 9000 content on OpenPA was written and completed in the early 2000s, updates slowly declined from then on, as did PA-RISC support in open and commercial operating systems. has been maintained in the two decades since to catch errors and add missing pieces here and there.


This site was started in 1999 when second-hand PA-RISC systems became affordable to collectors after being phased out for more modern 64-bit, Windows NT or Linux servers. Not a lot coherent PA-RISC information was 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 a collection of PA-RISC documentation available on the web from the 1990s — much of it from the Mach and MkLinux projects. Compiled into a basic web site (with frames!), the information was soon published on the web, with hosting provided by Bill Bradford of SunHELP. The late Mickey appeared soon after, with lots of input from the OpenBSD/hppa operating system.

After two years, in 2001, the site was renamed to and moved to its own Digital DECstation 5000 on 1Mb dialup. It has been written and maintained in vi (Nvi) in static HTML since, for more than two decades. The increasing support from HP for the PA-RISC Linux project made a lot official PA-RISC documentation available. Open source operating systems for PA-RISC made significant progress also, including version of OpenBSD and stock Linux. Most of the HP 9000/700 and many of the lettered workstations were documented on 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.

A spike of activity in 2008 resulted in lots of new content, with more PA-RISC systems such as the 64-bit 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 also, including third-party PA-RISC processors and OEM systems from Japan and some very-early 1980s PA-RISC computers. Update frequency and additions stalled considerably after 2008 with mostly low-intensity maintenance.


Major housecleaning has been done several times beginning from 2016 on, checking links and content and rewriting much of the original language. Some new additions included the PA-RISC timeline and prices, a new print edition and restructuring several sections. Many pages were changed or updated, some ideas from previous years (decades) reversed and some severely outdated text updated or removed. There is still some old and original content scattered throughout, and many ideas to be implemented.

Much of the original HP documentation disappeared during that last decade, removing most of the links to original sources and references. Interest and support in open-source systems seemingly dwindled also. There is still a story to be written around PA-RISC, HP 9000 and the opening up of the 1990s and 2000s. We’ll see.

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Paul Weissmann is the maintainer and author of OpenPA. Many people helped OpenPA with contributions and support over the years. Thanks go to:

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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 © 1999-2021 Paul Weissmann. No parts of this site may be reproduced or copied without prior written permission. Commercial use of the content is prohibited. Legal notes are on the Legal Notes page.

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The information on is based mostly on primary HP sources such as HP and PA-RISC technical reference manuals, handbooks and architecture documents from the 1990s. This was extended and correlated during the 2000s with secondary sources like magazine articles, news releases and journals like the HP Journal. Since many original sources and documents disappeared during the 2010s, much of the newer content of the last years is based more on secondary sources and industry articles.

PA-RISC CPU, chipset and architecture: Mostly made use of primary sources from HP, like the great HP External Reference Specifications (ERSs), and technical publications from HP CPU and chip design labs, that often were made available during the 2000s for HP-supported open source projects. Secondary sources in the form of articles or academic papers were used as well.

Computer systems: Information on the HP 9000 and PA-RISC computers is based on primary sources from HP and vendors in the form of system user guides, technical handbooks and architecture white papers. Also included in the research and collection were marketing brochures, news articles and industry reporting.

Operating systems: Depending on the system, either based on official vendor user and admin documentation as well as academic papers, talks, whitepapers and such. The heydays of open source, Mach, Linux and BSD research systems from the 1990s resulted in much information on public websites. Much of the operating system development on PA-RISC centered on the 1990s, information is getting sparse.

The Internet never forgets: A process that had started in the mid-2000s accelerated in the 2010s — many sources and information on the web from the 1980s and 1990s disappeared. Journals closed or lost their archives, websites vanished, companies merged and removed old documentation and websites in the process, and memory faded after all those decades. This pertained to most original HP documentation on HP 9000 and PA-RISC, contemporary news articles from the 1990s, news releases, price lists and so on.

It got quite difficult since then to write and update articles based on ever fluctuating sources. This might just be the transitional nature of the Internet, but it was surprising to see so much go after doing this for two decades.

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