PowerPC is a RISC instruction set architecture created by the 1991 Apple–IBM–Motorola alliance, known as AIM. Originally intended for personal computers, PowerPC CPUs have since become popular embedded and high-performance processors. PowerPC was the cornerstone of AIM's PReP and Common Hardware Reference Platform initiatives in the 1990s, but the architecture found the most success in the personal computer market in Apple's Macintosh lines from 1994 to 2006 (before Apple's transition to Intel).

PowerPC is largely based on IBM's earlier POWER architecture, and retains a high level of compatibility with it; the architectures have remained close enough that the same programs and operating systems will run on both if some care is taken in preparation; newer chips in the POWER series implement the full PowerPC instruction set.

History

The original POWER microprocessor, one of the first superscalar RISC implementations, was a high performance, multi-chip design. IBM soon realized that they would need a single-chip microprocessor and to eliminate some POWER processor instructions to scale their RS/6000 line from lower-end to high-end machines, and work on a single-chip POWER microprocessor, called the RSC (RISC Single Chip) began. In early 1991 IBM realized that their design could potentially become a high-volume microprocessor used across the industry.

IBM approached Apple with the goal of collaborating on the development of a family of single-chip microprocessors based on the POWER architecture. Soon after, Apple, as one of Motorola's largest customers of desktop-class microprocessors, asked Motorola to join the discussions because of their long relationship, their more extensive experience with manufacturing high-volume microprocessors than IBM and to serve as a second source for the microprocessors. This three-way collaboration became known as AIM alliance, for Apple, IBM, Motorola.

In 1991, the PowerPC was just one facet of a larger alliance between these three companies. On the other side was the growing dominance of Microsoft and Windows in personal computing, and of Intel processors. At the time, most of the personal computer industry was shipping systems based on the Intel 80386 and 80486 chips, which had a CISC architecture, and development of the Pentium processor was well underway. The PowerPC chip was one of several joint ventures involving the three, in their efforts to counter the growing Microsoft-Intel dominance of personal computing.

To Motorola, POWER looked like an unbelievable deal. It allowed them to sell a widely tested and powerful RISC CPU for little design cash on their own part. It also maintained ties with an important customer, Apple, and seemed to offer the possibility of adding another in IBM who might buy smaller versions from them instead of making their own.