Warp  wrote in message <44cdf9bd$1@news.povray.org>:
>    Now, the AMD64 is a special case: 64-bit binaries optimized for the
> AMD64 run slightly faster than 32-bit binaries optimized for the same
> processor. However, this speedup has nothing to do with the amount of
> bits used. It is because in 64-bit mode the CPU has enhancements which
> the binary can use for faster performance (the biggest enhancement is
> a bunch of additional CPU registers).

There is another point. I just remarked that the following code:

    for(i = 0; i <= N; i++)
	r += (double)i * (i / 100000000);

runs four to six times faster in 64 bits mode than in 32 bits mode on AMD64
or its intel clone, with gcc. This probably has to do with gcc using
different FPU mechanisms (SSE2 vs. x87). I am currently waiting for some of
my friends to test with different compilers and/or explain what they
understand of SSE2.

Post a reply to this message