Patent ID: 7840823

Claim:
A processor system including a processor which has an internal memory, an external memory, and a bus controller which controls a bus to which the processor and the external memory are connected, the system comprising: a measurement unit for measuring an instruction-execution rate of the processor; a clock controller for supplying the processor, the external memory, and the bus controller with clock signals having clock frequencies corresponding to the instruction-execution rate measured by the measurement unit, respectively; and a voltage controller for controlling a source voltage or a threshold voltage which are supplied to the processor, the external memory, and the bus controller, in accordance with the respective clock frequencies of clock signals supplied to the processor, the external memory, and the bus controller, wherein the clock controller has a comparator for comparing the instruction-execution rate obtained by the measurement unit with a reference value, and wherein the clock controller raises the clock frequencies of the processor and lowers the clock frequencies of the external memory and the bus controller, when the instruction-execution rate is not less than the reference value.