Ian, what 64 bit chipset uses 32 bit addressing ? That is by definition not a 64 bit chipset then, sounds very strange to me but it wouldn’t suprise me if you are correct that some do (probably Intel).
Go with AMD64 which was the orginal inventor of the EM64 extensions that Intel then “stole” (yes I know they can with the patent agreement from -94) and you’ll most likely be safe from such issues.
As for the prople coming here posting some printouts from various *nix systems, you really need to read the article again, this is NOT a Windows issue, my good, you are embarrasing.