If you have two CPUs, obviously, that would do it. Also, you could try running RC5 alongside SETI, with both at the same priority (RC5 is normally lower, but you can increase that.) That would make it about a 60/40 split, I think. Two RC5 threads (stupid idea normally) would assure something like a 30% share for SETI (and a 60% share for RC5 😀).