Abstract: A method for transmitting a power-saving command between a computer system and system chips thereof is described. A power-saving command associated with a first system chip is introduced to the computer system since a BIOS is modified therefore. The CPU of the computer system determines the power mode of the first system chip according to a register therein. As the first system chip enters the power-saving mode, the second system chip is informed entering the power-saving mode as well. Therefore, the peripheral devices coupled to the system chips can enter the power-saving mode smoothly so as to solve that the devices cannot enter the mode simultaneously since there is no power management unit (PMU) installed in the first system chip.