I've managed to run my Thunderbird 1.2GHz at 1.529GHz stable on my friend's IWill KK266 for about eight hours.. I took it to his house and ran it on his motherboard playing UT, Quake 3, and Half-life.. Never any problems at all. It was still running great when I took it out and went home with it. The highest I can get it on my current MSI K7T Turbo is only 1.477GHz, though.