AnandTech reviewed the Opteron 880 (Egypt) and Xeon MP 3.0GHz (Paxville) processors:
The current AMD platform hasn't changed much at all; the only change has really been the move to 1GHz HyperTransport. The K8 architecture is fairly old news now, but is certainly still more scalable and higher performing than Intel's offerings. Intel hasn't made any significant changes, though the E8500 chipset does use a dual shared bus instead of a single bus from the older Xeon MP chipsets. The shared bus helps the bandwidth bottleneck, but with more than 4 processor cores scalability really starts to slow. The diagrams below give a high level overview of the 4P architecture that AMD and Intel currently offer.