If you're looking into 64 bit than you better forget about Xeons and Pentium 4. Here is a good review of what you can expect by going to 64 bit from the two arhitectures. Pentium 4 is a dead end,was never intended to be a 64 bit processor, they had to do it because of the Opteron and the results don't seem promising.
Except for the synthetic benchmark of Sisoft Sandra, "optimized" for Pentium's EMT64, real life applications tell a total different story:
"Here we see a completely different situation than the results of SiSoft Sandra 2005 SP1. Athlon 64 processor runs 25% faster with 64-bit AMD64 extensions involved than in 32-bit mode. Intel Pentium 4 with EM64T, on the contrary, loses about 25% of its speed in 64-bit mode."
My hope was that with the release of XP x64 (and later LongHorn) and 64-bit PC systems, Dassault will get a move-on on a 64-bit version of CATIA (though that would probably be V6).
Dassault and IBM Announce 64-bit Applications for AIX
Dassault Systèmes and IBM have announced the first release of 64-bit enabled Product Lifecycle Management (PLM) applications for the IBM AIX 5L operating system. The applications are designed to provide 64-bit architecture capabilities for AIX Version 5 Release 14 (V5R14), which enables customers using ENOVIA DMU applications to perform digital mock-ups of full product configurations with a high level of detail and enables customers using CATIA V5 Structural Analysis to perform rapid finite element analysis on large assemblies.
Powered by IBM eServer pSeries systems, the 64-bit capability brings significant performance enhancement to users of CATIA Structural Analysis, ENOVIA DMU Navigator, ENOVIA Real Time Rendering and ENOVIA DMU Space Analysis for AIX 5.1 MIL 4.
