A computer system includes a power supply, a number of first power interfaces, a second power interface, and a voltage regulating module. The power supply includes a number of direct current (DC) voltage output terminals, to output a number of DC voltages to a motherboard of the computer system. The first power interfaces are connected to the DC voltage output terminals of the power supply, to output the DC voltages to first peripheral devices. The voltage regulating module includes an input terminal and an output terminal. The input terminal is connected to one of the DC voltage output terminals of the power supply, to receive the DC voltage from the connected DC voltage output terminal. The output terminal is connected to the second power interface, to output a regulated second voltage to a second peripheral device through the second power interface.