Hewlett Packards HP9000s are a line of servers and workstations first released in 1982.

Initial offerings relied on Motorola developed CISC processors but HP transitioned to their own PA-RISC CPUs before the decade was out to unify all non-PC machines under a single 32bit RISC architecture. A notable historical fact about the PA-RISC family of processors is that HP opted to go with larger L1 caches and omit L2 all together for the majority of these chips. Rather the caches were merged on-die with the processors and connected/synchronized via a bus.

HP decided to re-brand their existing model schema away from the established pattern (V-class, T-class, R-class, K-class, I-class, H-class, G-class, F-class, E-class and D-class) with the introduction of the processor they co-developed with Intel, the Itanium. From the year 2001 onward, rp-xxxx designates a PA-RISC based machine while rx-xxxx the Itanium counterpart. The eventual plan is to phase out all PA-RISC processors in favor of the Itanium by the year 2013 with 2008 being the last year HP9000s will have them as an option.

The machines originally ran HPs proprietary version of UNIX, HP/UX as a primary OS however NetBSD, OpenBSD and Linux have all subsequently been ported to run on HP9000s.

Hewlett Packards HP9000 homepage