A motherboard includes an I/O chip, a south bridge chip, and a delay circuit. The I/O chip detects a standby voltage on the motherboard and outputs an indicating signal that indicates whether the standby voltage is at high level. The south bridge chip is connected to the I/O chip to receive the indicating signal. The delay circuit is connected to the I/O chip and the south bridge chip. The delay circuit delays the indicating signal before sending the indicating signal to the south bridge chip.