The Xeon E5520: Popular for VMWare
Intel makes more than a dozen different speeds of the Xeon 5500 series processor. Why so many? One reason is that Intel divides them up into three different groups, based on their features. Within each group, there's 3 or 4 different models, each with a different CPU clock frequency.
"Kevin Houston recently asked which Intel Xeon 5500-series processor was most popular for running VMWare. My short answer: Probably the 2.26GHz Xeon E5520. Long answer follows..." This blog posting analyzes which Xeon 5000 series chip is best for virtualization.