Sorry to call you out on this, but IA64 is the Intel Itanium architecture, not 64bit x86 archtecture.
The naming is very confusing.
x86 (most common name)
IA-32 (Intel name - default in their manuals)
i386 (Linux 32bit stuff, including systems code)
i686 (Linux 32bit kernel level stuff)
AMD64 (AMD name - they invented it licenced it to Intel)
Intel64 (Old Intel name - still exists in older documents)
EMT64 (Extended Memory Technology 64bit) (New Intel name, following confusion with IA64 name)
IA-32e (Intel Architecture extensions) (Another Intel name, common in their manuals)
x86_64 (Common in most open source systems code - Xen, Linux etc.)
IA64 (Itanium Architecture)
A cynic might draw a comparason about some of the naming conventions and some of the silly obscure legacy components of x86.