Would x86 assembly work on x64 processors?

Question

Would x86 assembly compile on an x64 machine and still work properly? If not, what is the difference between x86 assembly and x64 assembly?

Answer 1

If by x64 you mean x86_64 (or amd64) and not IA-64 (Itanium), yes. It's intended to be backwards-compatible. However, you won't be able to take advantage of the additional instructions and hardware made available in 64-bit mode.

There are numerous additional features available in "long mode." 64-bit registers, additional general-purpose registers, SIMD features, larger address space, and so forth.