> I am using:
>
> CFLAGS+=-O2 -march=athlon
>
> in my /etc/mk.conf. But the problem is that I realized that I wanted
> this setting after compiling a large amount of software.

If you also add -fomit-frame-pointer, programs will run even faster.
But be careful with Mozilla/Firefox/Thunderbird. These crash with - 
fomit-frame-pointer.

Kind regards,
Adam