A method of operating a system on chip (SoC) includes calculating a first residence time indicating an amount of time that at least one task resides in an execution queue in the SoC, wherein the at least one task is assigned to at least one core of a multi-core processor in the SoC, calculating a total unit residence time indicating an amount of time that all tasks other than the at least one task reside in the execution queue, calculating a second residence time for the at least one core by adding the first residence time of the at least one task and the total unit residence time, and adjusting at least one of an operating frequency and a voltage of the at least one core based on the second residence time.