If the thornton normally runs at 166 fsb, that's the highest setting he should use. This board wasn't designed to overclock. I returned number 4 (that's right, I tried 4 different k7vta3's from Fry's) as it wouldn't post consistantly with a duron 1600 at any setting (100,133, or 166). If it did post, it was very stable while running the duron at 166 (2000).