C
Power PC
This appendix introduces another RISC processor, the Power PC, and discusses some of its
salient features. After completion of this chapter, the reader would know about
R Basic architectural details of Power PC.
R Instruction set and instruction format of Power PC.
R Essential features of Power PC pipeline.
O BJECTIVES
C.1 INTRODUCTION
Although the name of IBM is inseparable from the term IBM PC, we should remember that there is
absolutely no correlation between IBM PC and Power PC. As a matter of fact, the acronym PC is in no
way related with personal computers, but implies performance computing. Furthermore, the acronym
Power PC is the derivation from P erformance O ptimization W ith E nhanced R ISC – P erformance C om-
puting. To cut a long story short, Power PC is not a personal computer but an ef cient RISC processor
designed around super-scalar architecture, in the similar line of SPARC and UltraSPARC, but from a
different direction, which we would discuss now.
C.2 BACKGROUND
As back as in 1975, IBM was impressed about the upcoming RISC architecture and decided to use it
in its powerful workstations. The result was 801 and RT PC, which were made available in commer-
cial market during 1986. Although RT PC was not a real success, IBM continued to work with RISC
architecture based processors and brought out IBM RISC System/6000, another workstation based on
super-scalar architecture. At that time, IBM introduced the name POWER architecture and we already
know about the acronym POWER. Soon after this event, an alliance was formed between Apple, IBM
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