BareFeats has a benchmark, testing the SDRAM-based dual G4 at 1Ghz with the new DDR PC2100 ones. The new PowerMacs are the same or slower than their previous models, the test reveals. The Mac community got a bit dissapointed (judging from the forums). The author says that the slowdown is because the two processors share a 1GB/s pipe to Apple’s custom AGP/Memory controller. While the shared bandwidth is a factor, it is not the reason that makes the new Macs slower. Having a better look at the specs, show that the author have forgot a very important detail:The new PowerMacs have 1 MB of L3 Cache, while the SDRAM ones have 2 MB of L3 and that’s the real reason which results to the slowdown.
Especially his kinds of tests, that could fit a lot of their information on that cache, have a bigger impact when you have less cache. The author implies a technical “flaw” of the overall design, a hidden bottleneck, but this time I will have to semi-take Apple’s side, and say that this is not a technical flaw, but simply a design decision on the amount of L3 cache to be included.
Apple’s only mistake was to take this decision in order to decrease the price of the new Macs. Selling a slower Mac than the previous same model, it is just not good business these days for Apple.
New Macs might be a bit slower or the same speed as the previous same model Macs, despite the fact that they now using DDR. But this slowness is certainly not for the reasons the author implies (“shared bandwidth”).
Update: BareFeats have now updated their web site with the information about the cache, as presented here.
In other Mac news, Apple will coincide with next week’s release of Mac OS X version 10.2 (also known as Jaguar), consumers can buy a $199 a copy of the operating system and install it on up to five Macs in a single household