MUCH HAS CHANGED in the realm of server and workstation processors since our last round of tests, just before Intel's "Woodcrest" Xeon 5100 series debuted. Those Xeons have now made their way into the market, and AMD has countered with Socket F Opterons that promise higher performance and lower power consumption. More recently, Intel unleashed its new quad-core "Clovertown" Xeon 5300 series that aims for an even higher performance plateau.

As a result, the time has come for us to turn our attention once again to server/workstation-class processors and see how these latest offerings compare. To that end, we've employed a revised set of extensively multithreaded benchmarks and new methods for testing energy efficiency. What we've found is excellence on several fronts from both camps, in a market that is more tightly contested than ever. Read on for our results and analysis.