Microsoft favours AMD over Intel for Windows Server X64
 

WHILE INTEL has only recently started implementing its 64-32 instructions in its Pentium 4 processors - even though they've always been there and just needed to be switched on - its Xeon processors have implemented EM64T for quite some months now.
All the more surprising then, to look at Microsoft's minimum system requirements for Windows Server 2003 Standard X64 edition and to find the Vole appears to demand a much higher spec from Intel chips than it does from AMD's.

http://www.theinquirer.net/?article=22177