Power Mac G4 533 DP Still the King of Speed

when it comes to Macs. In our review of the new two-processor 533DP we proclaimed it the "King of Speed" at least until the newer 733 MHz Power Mac G4 model started shipping. We also quipped that it may shortly regain its title after Mac OS X v1.0 comes out since Mac OS X will support symmetric multiprocessing. However, it seems now, based on numerous reports, that the 533DP will not lose its crown any time soon.

The story was broken Friday and culminated yesterday in the completed comparo posted by rob ART morgan's Bare Feats and posts during the weekend and yesterday to Mike Breeden's Accelerate Your Mac forum. Not only did the 533DP test faster than or equal to the 733SP, as might be expected at least for MP aware applications, but the SINGLE 533 also beat the 733SP--incredible!

How can this be? The 733 MHz and 667 MHz G4 CPUs are a new PowerPC model, the Motorola 7450. The 466 and 533 are the older G4 models, 7410/7400. The new 7450's have a different architecture than the 7410/7400 with a smaller 256K L2 cache on the chip itself runing at the same speed as the processor and a larger 1MB L3 cache off chip running at about a third of the CPU speed. The 7410/7400 G4s have a large 1 MB off chip L2 cache running at half the speed of the CPU and no L3 cache. In theory, the new design should be faster so why isn't it? One theories is that the Mac OS 9.1 code is not yet optimized to the architecture of the newest model G4s. Maybe the L3 cache isn't being accessed efficiently. Who knows?

Unfortunately, this is a major issue for Apple just when it doesn't need another.