FC3 and Pentium 4 optimization?

[Steve Bergman]

I am seeking clarification of a point made in the release notes.  It 
states that FC3 is optimized for Pentium 4.  However the kernels and 
glibc available are labeled as i686 and i386.  I assume, since Pentium 1 
is the minimum hardware requirement, that the instruction set used is 
Pentium 1.  So:

1. What optimization and instruction set are the general packages 
actually compiled with?
2. What optimization and instruction set are glibc-i686 and  kernel-i686 
compiled with? (I seem to recall that the kernel is now optimized for size.)
3. How important is this to someone running a different processor? (Say 
Athlon XP.) IIRC p4 has very specific optimization requirements.

Thanks,
Steve Bergman