The PowerPC G3 series, which the PowerPC G4 series is replacing, currently tops out at 466MHz. Not counting Apple's advertising campaign, a G3 at a certain clock speed is often considered the overall performance equivalent of a Pentium III with 10-15% more MHz. The fastest G3 system Apple has shipped has a 450MHz processor. 466MHz G3 processors are only available in after market upgrades like the Newer Technology card we reviewed in our PCI PowerMac G3 Upgrade article.

So Apple's jump from 450 to 500MHz would seem like more of a hop than a leap in speed. As far as processor MHz goes, this is true. However, there are three important differences that make for significant and possibly huge performance boosts. The G4 has AltiVec, a more capable FPU, and can have a faster motherboard. What are all these things? Read on and find out.

The Velocity Engine is more commonly known as AltiVec. Think of Intel's MMX and SSE as well as AMD's 3DNow! rolled into one. If Apple is to be believed, AltiVec is faster than MMX, SSE, and 3DNow! combined, much faster. The various PhotoShop, video, 3D, and encryption demos Apple was showing at Seybold Seminar SF give Apple serious evidence to support their claim. AltiVec will require rewriting and recompiling to see big performance benefits, so Apple has made it as easy as possible to write for AltiVec by having Metrowerks support high-level language AltiVec optimization in their CodeWarrior development suite. With proper coding, in certain tasks, AltiVec can boost performance to the lofty level of one Gigaflop. For this reason, the US Government considers the G4 a supercomputer and will not allow Apple to export the G4 to certain nations. Apple probably doesn't mind losing the computer sales to China since they're gaining a wonderful PR tool.

The big question is, will developers support AltiVec? We think so. Unlike the PC, Mac developers have very little hardware they have to support. Instead of writing to EAX, A3D, and DirectX for audio, OpenGL and DirectX for video, and MMX, SSE, and 3DNow!, they just have to write to one audio API, one video API, and one extended instruction set. Already tens of audio, video, and graphics companies including Adobe have announced support or future support for AltiVec. It's like field of dreams. If you build super-fast DSP-like architecture in your CPU, they will come. Apple has been showing off tests where they claim a 500MHz G4 outperforms the 600MHz Pentium III by over a factor of two. At Seybold Seminar SF, we saw such speed gains in PhotoShop demonstrated. These major speed boosts were demonstrated over Apple's G3 hardware as well.