Nocona is an AMD64 supporting Xeon processor from Intel, but its much more than that as well. 1MB L2 cache is the lowest L2 cache size for the new range, and the front side bus has been ramped up from 533MHz to 800MHz. Also included is full support for DDR-II and PCI Express as a peripheral internconnect.
Hexus pits the Nocona against the AMD Opteron processor to see which is king. And although there are no 64-bit benchmarks this time, there are certainly some interesting 32-bit ones.
Without giving too much of the article away, I would immediately draw attention to the improvements made to this latest Xeon, which clearly have some effect. But is this enough to topple the mighty Opteron? You will have to read the article to find out.