A power source management system of a circuit board that comprises: a processor, comprising a core voltage input terminal; and a core voltage feedback terminal; and a voltage regulating member, comprising a setting terminal with a fixed reference voltage provided thereto; a detecting terminal connected to the core voltage feedback terminal to detect a feedback core voltage from the core voltage feedback terminal; and a core voltage output terminal connected to the core voltage input terminal to provide a core voltage thereto, wherein the core voltage is regulated by the voltage regulating member based on the feedback core voltage, such that the feedback core voltage is equal to the fixed reference voltage, wherein an offset voltage equal to a difference between a desired core voltage of the processor and the fixed reference voltage is provided between the core voltage input terminal and the core voltage feedback terminal by the processor.