I was having the same problem with my system the first time I turned it on.
I have an ECS k7s5a MB and a 1.2 tbird proc. and the 512 megs of pc133 ram
I turned it on and it read out as a 900mhz processor. I'm thinking what the ?! I checked the core on the chip, and it was labelled 1200, so I finally realized it was the bus speed. When you move it from 100mhz to 133, the core speed ups, and that's where the extra mhz comes from.
What I'm wondering is what the hell happens when I pull the pc133 out and stick in some ddr in the ddr socket? I mean, that's faster ram, right? Or is it just that it's double data rate, so it won't make a difference?