I was perusing slashdot and found this article which compares the Power Mac G5 with the new 64 bit Athlon CPU. Interestingly, their initial battery of tests suggests that the new Athlon chip is
substantially faster than the new Macs. Their tests are tough to compare since they are based on real world application performance. The problem is that applications are not always comparable across OSes since different teams usually write them and thus the final result may not be equivalently optimized across platforms.
Regardless, it is still impressive that the Mac is pretty much beaten across the board. So much for Apple’s rather dubious claim of having “the world’s fastest personal computer.” Still only time will tell.
One important thing the article mentions is that there is no 64 bit OS available for the new Athlon chip. This could potentially hurt performance especially since OS X has special 64 bit extensions to better take advantage of the new CPU. This makes the test results all that more impressive since the Windows machines are effectively running on an OS that is not optimized for the new CPU.