US Patent 7484112 Power management in a display controller

Managing power in a display controller having an on-board power supply coupled to a host device having an off-board power supply by way of a connector is described. If the on-board power supply is active, then power is supplied to the display controller by the off-board power supply by way of the connector and a low frequency clock arranged to provide a low frequency clock signal is turned on. Alternatively, when it is determined that the on-board power supply is active, then power is supplied to the display controller by the on-board power supply only, the low frequency clock is turned off and a high frequency clock arranged to provide a high frequency clock signal is turned on.