A baseboard management controller is disclosed. The baseboard management controller adapted to monitor a host comprises a baseboard management control module, a memory controller and a video graphic array (VGA) module. The VGA module comprises a video controller, a decoder, a select circuit and a mapping circuit. The decoder receives a transaction signal from a first local bus and decodes a first address signal contained in the transaction signal. The select circuit selectively transfers data from one of the microprocessor bus, the video controller and the memory controller back to the first local bus according to a control signal. The mapping circuit being connected with the decoder maps the first address signal and a second address signal to a third address signal, updates the first address signal and transfers an updated transaction signal.