I am wondering if running BOINC on Mac OS X in idle cycles of CPU really runs just on idle CPU cycles. Because at our Mac based grid we were thinking of running BOINC so that when we would not be using it fully BOINC could run on the rest. But as far as I know even making process running under nice 20 still does not make a process use just spare cycles. So our computations would be slowed down by some factor just because BOINC computing process would be running. So how does BOINC handle this?