An interview with some interesting tidbits of info for your reading pleasure over at Nordichardware

3DMark®03 doesn't natively support 64bit CPU's, HT, SMP or any CPU extensions. The reason for no 64bit support is that there aren't yet any end-user 64bit CPU's, not to mention 64bit supporting operating systems and 64bit compilers. However, DirectX 9.0 does have some SSE, SSE2 optimisations and some multithreading.