800MHz is overclocked, and the CPU obviously won't handle it. 680MHz is not overclocked, and it will work.
I have not used this, but I know the procedure. The CPU speed rollback is a lockup precaution. Once you set the speed, you must reboot the unit. If it comes up at the new speed, you must reset the speed again. If it doesn't come up, it is supposed to rollback to the old speed.
EDIT: Don't want to step on your post, heiko_s, but I agree. If it won't, why say it will?
Last edited by SurferTim
on Sat Jul 12, 2008 3:14 am, edited 1 time in total.