Last week I received a reference server with a couple Intel 3.6Ghz EM64T Xeon (Nocona) CPUs. These are the brand-new x86_64 chips from Intel, designed to directly compete with the Opteron. Intel may have borrowed heavily from AMD for the Nocona, but don't expect AMD64 code to run problem-free. The Windows 2003 64-bit beta won't install on a Nocona system, apparently due to a CPU check that occurs during the installer boot process. Similarly, RedHat Advanced Server for x86_64 U1 won't install, but U3 will.
I'm working on some benchmark testing of this system at the moment, and the results seem to indicate that the new chip has some solid floating-point chops, at least for 32-bit, and is the fastest Xeon processor yet released by Intel. 64-bit tests are to follow. It'll take awhile for code optimizations to catch up with the EM64T chip, but the 64-bit Opteron/Xeon shootout will definitely be interesting.
Hmm. Sun's heavily into the Opteron, HP and IBM selling Opteron-based servers, Intel has followed AMD's lead for the first time with the EM64T, and Microsoft's 64-bit Server product is in beta while RedHat and SuSE have solid x86_64 products available.
Interesting times indeed.