PCMark05 Favors Intel CPUs ?

I've heard rumors for years that performance in PCMark 2005 could change depending on what CPUID was handed to the benchmark, but this is the first opportunity I've ever had to test that theory. The term CPUID refers to a processor-specific character string that stores information on the chip's manufacturer, available features, make, and model. Different manufacturers use different CPUIDs, including GenuineIntel, AuthenticAMD, CentaurHauls, and the now-obsolete CyrixInstead. Intel and AMD both lock their CPUIDs to prevent them being changed by a third party, but VIA doesn't—and that gives us an opportunity to explore a question that normally can't be explored.


My my. Swap CentaurHauls for AuthenticAMD, and Nano's performance magically jumps about 10 percent. Swap for GenuineIntel, and memory performance goes up no less than 47.4 percent. This is not a test error or random occurance; I benchmarked each CPUID multiple times across multiple reboots on completely clean Windows XP installations. The gains themselves are not confined to a small group of tests within the memory subsystem evaluation, but stretch across the entire series of read/write tests.