The Hewlett Packard Precision Architecture is a CPU family and instruction set architecture (ISA). It was created in the mid 1980's as one of the first RISC implementations that wasn't a hand-waving fairy tale. The CPU survived quite a long time powering HP workstations and servers which ran HP-UX. Check Wikipedias PA-RISC page for a nice list of CPU models and more technical information.
Be aware that HP 9000 systems, as PA-RISC boxes are called, have multiple versions of system firmware and out of band access. Some use GSP firmware only. Some mix GSP features with MP features and also have an ILO (later models and most based on the PA8900). Accessing them can be tricky to the uninitiated. Obviously, we do it all the time here at PARSEC and could help you if needed.