I actually have a theory about MS's support for AMD64 in Windows. You remember that, originally, it was supposed to be ready about now. Then, all of a sudden, it became mid-2004.
Here's what might have happened. Intel might have said something to MS like,
"We'll have x86-64 (same thing) support in our mid-2004 version of Prescott. So, please delay support for it. We'll do the following for you:
asdfpom lgbnop okg ofd akhp gokj p' oarsf[g ppokmg apodf
(code for some horrible anti-competive thing that the FTC would love to know about)
Then, Intel found out that they couldn't get their AMD64 working until at least Tejas. And Linux starting eating into Microsoft.
Microsoft said, "Forget about it, we're supporting AMD64 in Q1, and not only that, we're supporting AMD's security extensions."
Petz