I was at microsoft.com when I came across this
http://www.microsoft.com/windowsxp/64bit/evaluation/top5.asp
If this is true in the home edition of winxp 64 then Amd might not have any trouble introducing dual core Athlon 64's.
Edit: This might have been posted before but I don't think so.
Here the linkMultiprocessing
Windows XP 64–Bit Edition is designed to support multiprocessing capabilities for maximum performance and scalability, supporting up to two symmetric 64-bit processors.
http://www.microsoft.com/windowsxp/64bit/evaluation/top5.asp
If this is true in the home edition of winxp 64 then Amd might not have any trouble introducing dual core Athlon 64's.
Edit: This might have been posted before but I don't think so.