Re: 32-bit vs. 64-bit x86 Speed

  George Peter Staplin <georgeps@xmission.com> wrote:


> This is an interesting claim. I've heard from several people that the
> 64-bit x86-64 architecture can be slower with some code patterns.


>From what I have heard, a 32-bit program compiled for a 64-bit CPU, will
in effect run in something alike 32-bit emulation mode. (A deliberate move
in the design of the 64-bit architecture, in order to avoid portability
problems.) So unless it actually has new code, directly rewritten as to
take advantage of the 64-bit architecture, it will in fact run somewhat
slower (of the CPU frequencies are the same).


If the program calls routines that are especially written for the 64-bit
architecture, for example number crunching, the speedup can be
significant.


    Hans Aberg

Return to the comp.compilers page.
Search the comp.compilers archives again.