So just as Intel puts off the release of its 64-bit processor, Microsoft acknowledges a 64-bit version of Windows Server 2003 that will work on Intel’s Itanium processor, but not on AMD’s 64-bit Opteron.
This is probably due to the fact that AMDs chips haven’t been available in prototype as long as Intels’. Microsoft will probably release Windows Server 2003 next month with built in support for 64-bit Itanium, 32-bit Opteron (Opteron has both 32 and 64-bit modes), with a promise of 64-bit Opteron capability as an add-on or a next release.