That's not enough... See also page 1 of this thread. The problem you have is power related.


Also, and has been written in this thread numerous times, start easy and then increase speed/pot settings.
So, start with two units at say 600Mhz, and dial mem and core pots back to the minimum while it still keeps running good.
Then increase frequency one or a few steps, and IF NEEDED, increase pots. If not, don't do anything. Repeat this process until you get at the desired or max feasible frequency on your system.