Int 10h, 12h /BL=36h    Select Video Refresh                              VGA

    Selects whether the video outputs to the display monitor should be
    enabled or disabled.

        Entry   AH = 12h
                AL = 0 | 1   Screen on | off
                BL = 36h

        Return  AL = 12h   If function supported


    Turning off the video screen is beneficial to the monitor when it
    is not in use. It protects the phosphor from being burned out at
    specific locations but does not require turning on and off the
    power to the monitor. It also improves data transfer speed from
    the host to the VGA.