A mainboard, display device, displaying method, and computer readable storage medium are provided. The mainboard has at least two display interfaces, a detecting circuit, and a processor. The at least two display interfaces are used for connecting to different displays. The detecting circuit is coupled to the at least two display interfaces, for detecting the electrical signal of the display. The processor is coupled to the detecting circuit, for determining information about the display connected to the display interface based on the electrical signal detected by the detecting circuit.