Power-saving computer system with a watchdog computer and method for controlling power saving of computer system with a watchdog computer

A first computer system including a first computer and a first display device is provided. The first computer includes a processor. The first display device is connected to the first computer and displays a graphics signal. The processor receives at least one of system state information and power state information from a second computer system including a second computer and a second display device, and generates a first power saving control command on the basis of the received state information. The processor transmits the first power saving control command to the second computer system. The first power saving control command is a command for controlling power saving of at least one of the second computer and the second display device.