Temperature control circuit for central processing unit

The present invention relates to a temperature control circuit for central processing units (CPUs) used for personal computers. A CPU temperature control circuit is provided that can vary the clock frequency and the power source voltage of a central processing unit (CPU) while the CPU meets the operational specifications. The comparison circuit compares the temperature of the CPU measured by the CPU temperature sensor with temperature information previously stored in the ROM The CLK and power-source control circuit switches the clock frequency from a high frequency to a low frequency when the temperature of the CPU becomes high. Then, the CKL and power-source control circuit switches the power source voltage from a high voltage to a low voltage at the time the timer counts up. When the temperature of the CPU becomes low, the CLK and power-source control circuit switches the power source voltage from a low voltage to a high voltage. Then, the CLK and power-source control circuit switches the clock frequency from a low frequency to a high frequency at the time the timer counts up.