Intel performed performance testing against Windows SharePoint Services 3.0 to determine how performance characteristics changed between the 64-bit dual-core Intel Xeon X5150 and quad-core Intel Xeon X5355 processors. This white paper presents their findings.

The test results in this white paper are intended to demonstrate the performance characteristics of several different Web server processor configurations in a Windows SharePoint Services 3.0 farm. Identical tests were conducted against the test farm with various combinations of dual-core Intel Xeon X5150 and quad-core Intel Xeon X5355 64-bit processors. In some tests, one core of a dual-core processor was turned off to simulate a single-core processor.

http://technet.microsoft.com/en-us/library/cc288087.aspx