Running 64-bit Win 2003 Server x64 and Win XP Prof x64 on AMD chips
The Windows 2003 Server x64 will only run on the AMD Opteron and not the AMD Athlon series. Whereas, the Windows XP Prof x64 will run on both AMD Opteron and AMD Athlon series. There is a movement now from the Opteron Socket 940 into the Socket 939 but I guess one will have to wait a bit for the Socket 939 Opteron chips. Socket 939 is relatively cheaper & with improved performance due to use of non-ECC & registered memory chips.
There is a nice article describing the use of AMD Opteron chips with Win 2003 Server x64 in a business situation (with Microsoft). Affordable 64-bit .NET computing is (almost) finally here!