I would use CPUTYPE=athlon in make.conf for that CPU. For gcc 4.2.x, these are your choices for x86/x86_64
If building kernel, you haven't got a lot of choice for the i386 arch. For that one, in the kernel config you'd have to use:
I don't mean to go against the rules here (I agree with that in general), but I don't mind people asking related questions in my threads. (In fact I don't consider it "my thread", I only started it). I spend a lot of time in forums, and sometimes in a thread something will inspire a question and it is practical to ask it there. It isn't necessarily thread hijacking. I believe this to be one of them. The topic did change since my original question... we got into CPUTYPE in make.conf and other make options.