PA-RISC Operating Systems
A broad range of operating systems was available over the years for PA-RISC workstations and servers. They are either Unix or Unix-like, with different designs having both been ported to and developed specifically for PA-RISC, including open source, research and commercial products.
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HP-UX: The story of HP-UX Unix started before PA-RISC, with versions for the early HP 9000 lineup — the HP FOCUS systems.
From the late 1980s on, HP-UX was available on the first PA-RISC server computers (800s), with HP-UX 7.0 released in 1989.
Updated and enhanced version soon followed, with the BSD-influenced HP-UX 8.0 and 9.0 from the early 1990s supporting most early HP 9000 700s and 800s.
The new HP-UX 10 was released a few years later, followed in quick sucession by 10.20 and 10.30.
Due to supposed Y2K issues in earlier versions, the very popular 10.20 was available free of charge for HP 9000 owners for a while.
The new HP-UX 11 versions were also released from the mid-1990s on, now with a
true 64-bit kernel, but still supporting most 32-bit PA-RISC systems.
Support shifted soon to the newer lettered and rp/rx computers with the early 2000s 11i HP-UX versions, which integrated PA-RISC and Itanium into a single stream with 11i v2.
NeXTSTEP: NeXTSTEP on PA-RISC was a commercial Mach-based operating system from the 1990s with an Unix userland and a then extremely modern GUI, ported to PA-RISC in 1994. Support for some 32-bit PA-RISC machines was available in Version 3.3, with limited hardware support.
R&D: As soon as PA-RISC was released in the late 1980s, academic and industrial research projects started operating systems ports to PA-RISC. The premier among them was HPBSD from the University of Utah (Mike Hibler) which was a port of 4.3BSD and later 4.4BSD to early 800s servers and specially the early 700s workstations. HPBSD contained commercial AT&T and HP code, and was never freely available. Several ports of the Mach microkernel were undertaken during the early 1990s, with HP Tut porting Mach 2.0 and the University of Utah both Mach 3 and Mach 4. These Mach ports were never really used widely as production systems, but formed the basis for other research projects and later the BSD and Linux ports.
MK-PA: Porting efforts for OSF/1, the proposed Unix operating system by an alliance of DEC (Digital), IBM, HP and others to compete with AT&T’s and Sun’s System V Unix, started around 1990 by HP itself with HP OSF/1 and in the mid-1990s by the OSF RI Open Group Research Institute with several releases of MK-PA (OSF/1). MK-PA never had really wide distribution and was discontinued in the later 1990s.
Linux: Early Linux work built upon the rather unstable MkLinux, a research project from the mid-1990s by the Open Group/OSF to port a Linux kernel onto a Mach microkernel, which in turn built on the previous MK-PA OSF/1 port to PA-RISC. The native Linux port to PA-RISC was originally started in 1998 and gained momentum after HP started helping with equipment and more importantly, documentation, in 1999 and quickly superseded the earlier Mach-based MkLinux. Because of HP’s assistance, the machines targeted at that time were newer than what other ports supported, like the A180, B180 and 64-bit PA 2.0 systems.
PA-RISC support was included in the mainstream kernel, and shipped with Debian and Gentoo distributions as official ports. During the 2010s however, support declined and development was scaled back, resulting in the eventual removal of PA-RISC from official distributions. PA-RISC Linux still has the broadest support for systems and hardware from the current open source efforts.
BSD: Work on an OpenBSD port to PA-RISC on HP 9000/700 systems was started by Michael Shalayeff Shalayeff around 1999. His porting efforts were based a lot on source code and information from the previous PA-RISC research projects Lites/HPPA and MkLinux. The first complete OpenBSD/hppa release was version 3.5, with PA-RISC having been supported since on most 32-bit workstation, some 64-bit workstationss and some servers. An OpenBSD/hppa64 port to support PA-RISC 2.0 computers running natively in 64-bit mode was started in 2007, but never took off.
NetBSD/hppa is a free, open source Unix-like operating system, and supports PA-RISC
computers since around 2005, called NetBSD/hp700 until the 7.0 release, as a
Tier II port.
The port focuses on 32-bit PA-RISC 1.1 computers and 64-bit PA-RISC 2.0 systems in 32-bit.
The current effort is largely based on Michael Shalayeff’s work on the
OpenBSD/hppa kernel from 2004 to 2005 and updated OpenBSD code later on.
There were a few other notable operating systems that ran on PA-RISC. HP’s own MPE business mainframe operating system was ported from the HP 3000 CISC platform to PA-RISC with MPE/XL and MPE/iX, with several releases from 1988 to 2002. Another PA-RISC operating system by HP was HP-RT, a real-time operating system geared towards the HP 9000 740 series VME board workstations.
Third-party operating systems for PA-RISC were developed by several companies for their own line of computers. This includes Convex SPP/UX, a heavily modified Mach-based operating system, which looks familiar to HP-UX but is a completely different design, for the Convex/HP Exemplar SPP1000, 1200 and 1600 line of mainframes. The fault-tolerant Continuum servers from Stratus were shipped with either Stratus FTX, a System V Unix, or Stratos VOS, a transaction-processing oriented system.