Mac Musings

Future of the PowerPC

Part 2: PowerPC Today and Tomorrow

Daniel Knight - 2002.05.01 -

Yesterday we looked at the history of the PowerPC: The AIM consortium, the theoretical benefits of RISC, IBM's POWER architecture, the evolution of the PPC up through the G3 and G4, and how Apple lost the Megahertz War. Today we'll look at ways for Apple to move forward.

Multiple Processors

If you look at the world of powerful computers, you'll find several features that make them fast, powerful, robust, efficient, and scalable. They may have redundant power supplies, arrays of hard drives, and multiple processors. It's the latter I want to look at here.

Round 1

DayStar was the first to offer multiple processors on the Mac platform with their Genesis MP. This powerhouse was similar to the Power Mac 9500 in many respects, but it was built into a tank-like enclosure and always had two or four 604 processors. The fastest Genesis, the MP 600, had four 150 MHz CPUs.

Next came the Genesis MP+, which used the more efficient and higher speed 604e processor. The top model was the 928, which has four 233 MHz 604e processors. In comparison, Apple's dual processor 9600/200 MP (2x200 MHz) was a slacker, and the faster SuperMac S900 250MP (2x250 MHz) was only a little better.

But unless you were running Photoshop or another specialized program, you couldn't take advantage of multiple CPUs. Photoshop mavens loved the quad-processor Genesis, but the G3 processor eventually eclipsed even the MP+ 928 - and the AltiVec-enhanced G4 blew it into the weeds.

Round 2

The G3 was always intended as a consumer CPU, but the fact that it was optimized for real world code and handily outperformed the 604e turned it into the choice for Apple's "pro" models, at least until the G4 was ready. Alas, the G3 was not designed to function well in a multiple processor setting.

The G4 was, and Apple made the best of it with the "two brains are better than one" Power Mac G4 MP series introduced in July 2000. This was also Apple's only way to offer more than 500 MHz performance, since Motorola was stuck at the 500 MHz mark.

As Motorola produced faster G4s, Apple tried to marginalize dual processor models by only offering it with a slower CPU. Even today Apple only offers a single dual-processor model, although now it is their fastest Power Mac.

Meanwhile at IBM

And let's not forget the IBM Power4, a CPU related to the PowerPC and already running at 1.0-1.3 GHz. The Power4 is especially designed for a multiple processor environment. IBM's "entry level" models based on it use 8 CPUs - and the top-end machines run 32 processors.

Looking Ahead

The Motorola Option

Apple can continue to depend on Motorola, a company that remains at the trailing edge of CPU speed. We can rest assured that sometime soon Motorola will manage to break the 1 GHz barrier, just as they finally broke the 500 MHz barrier in 2001.

Apple can push ahead by offering more MP (multiprocessor) models, such as a reasonably priced dual 800 MHz G4 machine (one was recently discontinued) and a quad-processor model providing Pentium-stomping power from four 1 GHz G4s.

And they can also wait for Motorola to produce the next generation PowerPC processor, which will probably be known as the G5.

The IBM Option

The alternative is to team up with IBM to develop a next generation CPU that can immediately run at 1.4 GHz, readily supports lots of processors (like IBM's POWER series), and lacks Motorola's AltiVec functions. We'd basically be looking at a G3 twice as fast as any sold today that also supports multiple processors.

The kicker is losing AltiVec, which is part of the reason OS X, Photoshop, iDVD, iMovie, and many other programs run much better on G4s than G3s. But IBM is convinced that adding such functions to a CPU is a mistake, adding performance in one area while the rest of the processor gets no boost at all. In fact, AltiVec may be a big reason Motorola has been unable to produce faster G4s.

Apple may be able to convince IBM to license AltiVec from Motorola, but another option would be to create a new velocity engine for the new CPU. It wouldn't have to be nearly as powerful as Motorola's AltiVec, since it would already be running 40% faster. And if AppleDesigns the next generation motherboard for it, improving performance could be as simple as dropping in another CPU - or a whole bunch of them.

If IBM were to design a supercharged G3 capable of running at 1.0-1.4 GHz now (and 2.0 GHz in the future), supporting multiple processors, and including a "velocity engine" half as efficient as AltiVec, Apple could have a real alternative to Motorola's MHz stranglehold.

The Third Way

Another option would be for Apple to team up with IBM to produce a G3 capable of supporting multiple processors and running a GHz speeds, but without any velocity engine. The next generation Power Mac motherboard could be designed to accept either the IBM or Motorola processor - or a combination of G4s and IBM's new CPU. It might take some recoding of OS X for it to understand that some CPUs may have AltiVec while others don't, but this scenario has great potential, especially if the system is also designed to handle processors at different clock speeds.

I think Apple and IBM would have a great deal to gain from adapting IBM's POWER technology and MHz lead to the next generation of Power Macs.