There is definitely a config file for building a stock RedHat kernel with Athlon optimizations, as Drakken said. For 7.2 at least, there is also an RPM with a binary optimized for Athlon. The RedHat install detects the Athlon cpu and installs the appropriate kernel.
I know this because a stock install of 7.2 on my Iwill KK266 won't boot due to problems with Athlon optimized kernels and some Via chipsets. I had to significantly underclock my box to boot up with the Athlon kernel, so I could then build a new one.