The BOINC throttle set through the "use at most x% CPU time" option presently is not as as smooth as many would prefer. Typically the World Community Grid default for the standard pre-set profile is 60% meaning the science runs for 3 seconds at 100% and pauses for 2 seconds, giving an average 60%. This is good for thermal control, but can result for some for the cooling fans to continuously switch on and off, especially laptops, which are more heat sensitive.