MoooIts just TF2. I have a AMD 965 BE (OC at 4.1) with 16GB DDR3 1800 RAM and an ATI-7970 graphics card. I still have trouble maintaining stable 120-130 fps. Oh and i use dx9frames config too.
I play BF3 and Blacklight Retribution at 250-290 fps but tf2 jumps anywhere from 55 to 170.
happens to me too
I can get over 100 200 fps in other games, hell my computer can do 40fps stable in metro 2033 maxed out at 1080p, but tf2 goes down from 50fps and then up to 120 (cap it at 132, probably could go to 400fps at some times).
Ithink its just because tf2 is badly optomized, and more cpu reliant.