Two totally different approaches. PA-RISC is the Reduced Instruction Set Computing, used in HP-9000 servers, which are based on relatively current technology.
Mainframes are big, rellics used for legacy applications and government. The technology is not on the same level as your HP-9000 server. They do perform important functions, and IBM continues selling them I believe.
Alas, HP has announced it won't be developing new PA-RISC based servers, so both will someday be obsolete.
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Steven E Protter Owner of ISN Corporation http://isnamerica.com http://hpuxconsulting.com Sponsor: http://hpux.ws Twitter: http://twitter.com/hpuxlinux Founder http://newdatacloud.com
Mainframs are Complex Instruction Set Computers (CISC) whose instructions set were defined int the 60's and 70's. At the time, high speed instruction/data caches hadn't been invented. The could microcode the processor to do muliple instructions in a cycle before the next instruction or data could be fetched from memory, so it was more efficient to have CISC design. That has obviously changed over time, and so have the original factors that drove RISC designs. The first pa-risc chip had .5M transistors, and now there are hundres of millions of transistors on a chip. The newest technology is EPIC, although SUN is trying to just cram more slow processors into a single chip, and do four way threading of each CPU. This is okay for some applications, but fail badly for others.
