64-Bit Compiler Compadibility

[Guest Syntax]

This thought came across my head recently. All of the processor vendors are starting to show off their 64-Bit CPU's for home & business use.

 

My question is, does anyone know if the original x86 compilers will compile efficient code on the new 64-Bit processor? Most claim to be native to x86 as well as their new instruction set, but some (Itanium & Itanium2) claim to simply "emulate" the 32-bit enviroment, which would mean that just about all compilers will produce inefficient, crappy code on them. If Intel plans on dominating the server market, and the servers are running older x86-oriented software (Apache, Linux, etc), then will the processor even add power? Or take it away in a sense?