Hitachi SR2201 processing unit

A licensed instruction set with a local answer bolted on. Hitachi implemented HP's PA-RISC, then added what it called pseudo-vector processing: hardware that prefetches long vectors into registers so that streaming code does not pay the cache-miss penalty that normally makes RISC processors disappointing on physics workloads. This is the compromise of the mid 1990s in one part. Vector machines were fast on the science but priced themselves out, and RISC was cheap but stalled constantly on exactly the access patterns lattice QCD generates. CP-PACS was designed by physicists who needed the second option to behave like the first.