Mine is set for "Optimal". When I set it manually, which is rare, I keep it at least 85Hz if possible since I can see flicker at 75Hz on my big screen (19"😉. I'm not sure what my combination is capable of for a maximum, but with my NEC and the Radeon, it's probably around 110-120Hz at 1280x1024x16 (or 32, can't remember).