AMD got the attention of Microsoft with their 64-bit Athlon 64/Opteron platform, and it was enough attention to warrant a new OS port to x86-64. Just weeks ago AMD scored another victory, with Intel announcing the adoption of AMD's 64-bit extensions to x86.
Future Xeon and Pentium 4 processors will ship with the x86-64 extensions enabled but architecturally they will be identical to the currently available Prescott based Pentium 4. The architectural similarity between Intel's IA-32e ad IA-32 processors (IA-32e is Intel's marketing equivalent to AMD64) is an important point to note as it means that if Opteron is able to outperform Xeon in 32-bit mode, it will maintain a performance advantage in 64-bit mode as well. We are assuming that Intel has no specialized hardware to improve 64-bit performance over AMD's solution, so the Xeon vs. Opteron comparisons we've brought you in the 32-bit world should still hold true in the 64-bit world later this year.
There has been much editorializing about Intel's recent 64-bit announcement, and we'll add nothing more than this to it all: it's a very good thing that Intel has gone the x86-64 route, it will mean that we see software support, drivers and overall market acceptance sooner. We have AMD to thank for Intel's backing x86-64, which is a big feather in AMD's cap but if there's one thing to be said about business it's that there's no room for pride. Intel made the right decision; they would be losing sales if they didn't adopt x86-64, leaving those who needed a 64-bit x86 solution no option other than Opteron. However Intel gives AMD nothing if they adopt x86-64 in their own CPUs; AMD's sales don't increase and remember what we said about pride in business.
News source: anandtech