sorry the ignorance but, is it or not, that video cards can do more then 100 fps per minute, so if in a certain part of rendering the image cpu or whatever goes slower and needs more power, the frame rate can go down with a safe margin. It the video card does 100 fps, if a more detail part of the level/game do the video card go down, the 100 fps is a safe margin, it could go to 80 or 60 and still mantaine a good level. Am i wrong?Not laggy at all mate... after all science has proved the human eye can't see beyond 60fps anyway!
Most games run around 95-110fps no problems.