

A short history of the PowerPC as a desktop processor

16. april 2008

In 1994 I switched from DOS/Windows to the Mac, my first Apple computer was a PowerMac 7100AV with 16 MB Ram and a 500 MB harddisk (quite a lot back then). It was the first generation of Macs using a PowerPC processor (prior models used Motorola 68k CPUs) and it ran System 7. 1. 2 (they didn't call it "MacOS" yet if I remember well).

PowerPC is a RISC microprocessor architecture created by Apple, IBM and Motorola in the early 1990s. It's largely based on the earlier IBM POWER architecture and the Motorola 88k bus, it was designed to be a desktop CPU but today it has also become a quite popular embedded CPU. Apple used the PowerPC in their Macintosh computers from 1994 to 2006 (when they transitioned to Intel x86), and a lot of popular game consoles are also based on the PowerPC architecture, including the Sony Playstation, the M$ Xbox 360 and the Nintento Wii for example.


The processor in my PowerMac 7100 was a PowerPC 601 running at 66 Mhz - using a RISC processor in a personal computer was quite new in the mid 1990, although Acorn already developed RISC home computers in the 1980s (the famous Acorn Archimedes which later became the RiscPC).


IBM first introduced POWER with their RS/6000 in 1990, it was a quite expensive superscalar, high performance multi-chip design. Shortly after they started work of a less expensive single chip design. IBM approached Apple with the goal of collaborating on the development, and finally Apple brought Motorola on board (Motorola was the maker of the highly successful 680x0 processors which were used in Apple Macs, Commodore Amigas, Atari STs and even early Silicon Graphics workstations).

The first PowerPC processor was the PowerPC 601, which offered full compatibility with the existing POWER architecture (this was dropped with later generations). It was used by Apple for their new PowerMac computers, both IBM and Motorola offered PowerPC based computers, Microsoft released Windows NT 3.51 for the architecture, IBM ported AIX and announced OS/2 while Sun Microsystems ported Solaris to the new platform. Everything looked good for the PowerPC as a new desktop architecture back then, and many experts even thought this could be the end for Intel and the x86 platform (in fact the PowerPC 601 was also faster than any Intel chip at the time).

But finally IBM didn't manage to port OS/2 to the PowerPC, and in the end only Apple was successful on the market with their line of Power Macintosh computers. Support by other solution providers vanished and plans to port other OSes were cancelled. Both IBM and Motorola started to focus their PowerPC efforts onto the embedded market.

The second PowerPC generation included the low end PowerPC 603 and high end PowerPC 604. The 603 didn't perform well when running Apple's OS because the built-in cache was too small for the required 68000 code emulator, therefore Apple had to wait for the improved 603e before they could use the PowerPC in a laptop (that was the PowerBook 5300 series - I owned one of those, and I can confirm that this was probably the worst product Apple ever produced). There was a 64 bit implementation called the PowerPC 620, but Apple never used this chip as it was quite slow and expensive.

There were also rumors about a PowerPC chip with a built-in Intel x86 emulator that would allow M$ Windows emulations to run at native speed. This project, dubbed the PowerPC 615, did in fact exist as IBM developers at IBM's Essex Junction, Burlington, Vermont facility worked on it in 1993. There were even running prototypes of the chip in 1995, but the project was cancelled shortly after because of performance problems. There are also rumors that Microsoft convinced IBM to drop the development of the 615.

The third PowerPC generation (aka PowerPC 7x0 or simply G3) was based on a greatly improved version of the PowerPC 603, and the fourth generation (aka PowerPC 74xx or simply G4) by Motorola used the PowerPC 604 core design with an additional SIMD / vector unit. Motorola had massive problems with the manufacturing of the G4, and finally Intel was able to surpass the PowerPC in terms of speed and performance.

Apple was in big trouble then, and users had to wait a long time until IBM finally introduced the PowerPC 970, a 64 bit implementation using a POWER4 core (the POWER4 was a multicore design in fact) with an additional AltiVec compatible SIMD unit. It looked as if the PowerPC was finally back to the desktop, but shortly after IBM experienced the same problems as Motorola before.

In 2006 Steve Jobs finally announced that Apple would migrate to the Intel x86 platforms. It is said that nobody at IBM was informed about this move, and IBM managers responsible for the PowerPC development learned about the switch in the news.

The PowerPC remains a successful embedded and game console architecture today, and many supercomputers in the Top500 list are running PowerPC or POWER processors. But on the desktop the PowerPC is definately dead.