Chapter 1: PA-RISC Architecture from HP
PA-RISC stands for Precision Architecture, Reduced Instruction
Set Computing; RISC contrasts with CISC.
Hewlett-Packard was the first computer company bold enough to
replace their entire CISC machine families with RISC
machines and migrate
their users to the new, faster architecture. When HP attempted
this it was revolutionary: now RISC is the conventional design
for new high-speed chips.
A good way to learn about PA-RISC is to read the excellent
book Beyond RISC.