There are now three 64-bit implementations in the “Intel® compatible processor” marketplace:
Intel IA64, as implemented on the Itanium 2 processor
Intel EM64T, as implemented on the Xeon DP “Nocona” and future Xeon MP processors
AMD AMD64, as implemented on the Opteron processor
There is some uncertainty as to what a 64-bit processor is and even more importantly, what the benefit of 64-bit computing is. This document introduces the EM64T and AMD64 architectures and explains where 64-bit processing is useful and relevant for customers in this marketplace.
While this is not really virtualization related, VMware start supporting 64bit architectures, so this reading could be interesting for some of you.