PA-RISC Processors

PA-7100/PA-7150 (PCX-T)


The PA-7100 was the first PA-RISC processor to integrate the Integer ALU and FPU on a single die. It was introduced in 1992, with the enhanced PA-7150 in 1994. The design of the integer units is close to the PA-7000 but modified to scale to higher clock speeds. The previously external FPU was a new design and moved on chip, taking about one third of the transistor count. The link between the PA-7100 and its instruction cache was doubled in width compared to the PA-7000. The PA-7100 is a superscalar processor that is able to issue two separate instructions at a time. It was used in a large range of 1990s HP 9000 workstations and servers.

Multi-processor systems could be designed with two astrategies: either two PA-7100s attach to a shared PBus and one Viper Memory and I/O Controller, or each PA-7100 is attached to its own MIOC, which in turn is attached to a shared memory and I/O bus with the other PA-7100/MIOCs.

The PA-7150 is a PA-7100 with tweaks to the core and cache subsystem to allow clock frequencies up to 125 MHz.


Used in


  1. A 200 MFLOP HP PA-RISC Processor (.pdf) W. Jaffe, B. Miller, J. Yetter (1992: Hewlett Packard. Proceedings of IEEE Hot Chips IV)
  2. Multiprocessor Features in a PA-RISC Processor Interface Chip (.pdf) T. Alexander et al (1992: Hewlett Packard. Proceedings of IEEE Hot Chips IV)
  3. Évolution des gammes de processeurs MIPS, DEC Alpha, PowerPC, SPARC, x86 et PA-RISC (PDF) André Seznec and Thierry Lafage (INRIA: June 1997)

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