The most astonishing thing about this is it was done under forbearance of the ISA.. PA-RISC ISA was basically frozen in 1996 and they were able to ride that at the top for years. For instance PA-RISC doesn't really have appropriate instructions for desirable atomic operations. But it led to working on the right problems, a hardwired control RISCy chip that happened to be philosophically similar to the survivor POWER.