Mac Musings

Quartz Extreme Empowers the G3

G4 Insignificantly Superior to G3 Revisited

Daniel Knight - 2002.12.31

Almost three years ago I penned a contrarian piece, G4 Insignificantly Superior to G3, in which I tried to cut through the marketing hype and explain that for the Mac OS itself and almost every Macintosh application of the time (Photoshop being the best known exception) the G4 provided no significant improvement in performance over the G3.

Today the picture has changed a bit. Apple has moved everything except for the last remaining 600 MHz CRT iMac and the iBook to the G4 processor. In addition to Photoshop, programs such as iTunes, iMovie, and iDVD harness the power of the AltiVec velocity engine inside the G4 processor. But for those still using OS 9 as their primary operating system, the G4 remains insignificantly superior to the G3 - except in the realms of audio, video, and graphics editing.

Of course, the fastest G3 model runs at 800 MHz, and the G4 is available in a dual 1.25 GHz model with a 2 MB level 2 cache, so there are some raw horsepower differences, but putting a 700 MHz G3 iMac against a 700 MHz eMac or G4 iMac under OS 9.x will result in comparable performance.

OS X Changes Everything

What we didn't have three years ago was Mac OS X. Apple's latest, best ever operating system takes full advantage of the velocity engine, especially when handling screen displays. From the beta through 10.1.5, Mac OS X itself was a good reason to have a G4 instead of a G3. (Again, except for applications such as audio, video, and graphics editing, most applications don't really care which CPU your Mac has.)

This was part of the accepted wisdom until Jaguar shipped and users had a chance to experience Quartz Extreme. For the best OS X performance prior to Jaguar, you wanted lots of memory, a fast hard drive, a good video card with plenty of memory, and a G4 processor (or two).

Quartz Extreme Changes It Again

Now we have come full circle. With Jaguar, Apple introduced Quartz Extreme, which moves the display processing from the Mac's CPU to the ATI or Nvidia graphics processor itself. Suddenly it became more important to have supported video for optimum OS X performance than to have a G4 processor.

For better or worse, Quartz Extreme requires 16 MB of video memory (and wants 32 MB for best performance), AGP 2x video (4x recommended), and a supported ATI or Nvidia graphics subsystem. Although some users with older Macs, especially the beige G3, have attempted to use Quartz Extreme (QE) with an otherwise qualified Radeon PCI video card, the PCI bus just doesn't have the bandwidth QE demands.

For the most part, this means most older Power Mac G4s can be upgraded for full QE support. Only the Power Mac G4 supports the AGP bus, and you have to make sure you don't have the Yikes! model that only supports PCI video. The PowerBook G4, eMac, and G4 iMac all support AGP 2x, but the CRT iMac does not.

The May 2002 iBooks had AGP 2x with 16 MB video memory, making them just powerful enough for Quartz Extreme, but the November 2002 iBook improves things with ATI Mobility Radeon 7500 video and up to 32 MB of VRAM, providing optimal QE support.

Suddenly the lack of the G4's velocity engine becomes far less significant. Sure, iTunes will rip a bit faster with a G4, and some Photoshop filters will work faster with a G4, and burning DVDs still requires a G4, but for most users most of the time a G3 with full Quartz Extreme support is more than adequate.

Future of the G3

This gives the G3 a new lease on life. IBM has the ability to produce 1 GHz G3s - and probably faster ones in the near future. The only significant differences between the G3 and G4 are that the G4 supports multiple processors and has AltiVec. Entry-level Macs don't use multiple processors, and Quartz Extreme minimizes the benefit of AltiVec as far as the display system is concerned.

If Apple wanted to, they could update the G3 iMac to 800 MHz (or even 1 GHz), put in Radeon 7500 video with 16 MB of video memory, and have an immensely perky entry-level computer selling for US$800 or so, the same price as today's 600 MHz G3 iMac.

We've come full circle. Where the G4 was definitely superior under OS X 10.0 to 10.1.5, that's no longer the case for Macs that support QE. The G4 still has some advantages under Jaguar, but they are less significant than they used to be.

Thanks to QE, the G3 may still have a future. Until now, the accepted wisdom was that the G3 was dead, but that needn't be the case. I don't see Apple moving the eMac or flat panel iMac backwards to the G3 (there are other benefits the G4 has, including faster memory handling), but this could keep the CRT iMac alive and already makes the iBook responsive and affordable.

A fast, low cost G3 CPU plus Radeon 7500 graphics could also be the heart of that very affordable modular desktop Mac we keep hoping Apple will produce.

Sure, someday we'll have a G5 or IBM's PowerPC 970, but until then, the range from the G3 with Quartz Extreme on the low end to dual processor G4 machines on the high end gives Apple and Mac users all the power most of us need.