Four-Way Superscalar PA-RISC Processors
Anne P. Scott, Kevin P. Burkhart, Ashok S. Kumar, Richard M. Blumberg, Gregory L. Ranson · 1997
The HP PA 8000 and PA 8200 PA-RISC CPUs are the first implementations of a new generation of microprocessors from Hewlett-Packard. The PA 80001-3 is among the world’s most powerful and advanced microprocessors, and at the time of introduction in January 1996, the undisputed performance leader. The PA 8200,4 introduced in June 1997, continues this performance leadership with higher frequency, larger caches, and several other enhancements. Both processors feature an aggressive four-way superscalar implementation, combining speculative execution with on-the-fly instruction reordering. This paper discusses the objectives for the design of these processors, some of the key architectural features, implementation details, and system performance. The operation of the instruction reorder buffer (IRB),5 which provides out-of-order execution capability, will also be described.