Folding@Home will use the full capacity of your CPU, even more so than some other programs that run it at 100%, because it stresses various subsystems within the CPU that other programs (games, some DC clients) don't touch. If your CPU is unstable while running F@H (i.e. you get GROMACS WU terminations), you should back off on the overclocking slightly and/or work on better cooling, because work from an instable CPU could potentially get corrupted and is not useful to the F@H project (you will get partial credit for it, however).