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Old 20th September 2002
Lives for gear

I found this to be a fascinating look at the new DDR ram based Macs vs the up-till-now SDR based Macs:

A couple of things, if you please. First, this is a Mac oriented site. Secondly, yes these are G4 vs P4 vs Athlon based benchmarks, but the point of interest is the standard G4 vs the XServe at 1GHz. That is basically DDR vs SDR, in the main.

Bottom line, really, is that DDR in the new Macs is all about marketing, none about performance. Why? Because on the PC side, systems using DDR also have the equivalent of a DDR based Front Side Bus. It's xfering data at double (or for the P4 and Rambus x4) of the actual FSB clock speed.

For whatever reason, this has not happened with the new DDR based Macs, and the FSB is still 133 or 166MHz. The DDR ram is quoted in the Apple press release as being 333MHz. Correct. Unfortunately, it sits around waiting for the half as fast FSB, to little useful effect.

The net result, as you can see in the independent benchmarks, is that the XServe with DDR is no faster than the (old) G4 with SDR. A little slower here and there, actually, since latency is also a factor. FSB on both of these boxes is 133MHz as opposed to the 1.25GHz, which is 166MHz.That should help the 1.25 a bit more.

And though it's not the real issue in this thread, the benchmarks also show two other things. First, why AMD has so many fans on the PC side. Second, Apple obviously carefully cherry picks which Photoshop tests they use in order to be "90% faster".

On a related topic, it does appear that IBM and their new "GigaProcessor Ultralite (GPUL)" is the frontrunner for the next generation Macs. It's a 64 bit CPU. No idea of a timetable yet. It appears the G5 may not happen, or in any event, happen soon enough.

Brian T