INT 10 - VESA SuperVGA BIOS v1.2+ - GET/SET DAC PALETTE CONTROL
        AX = 4F08h
        BL = function
            00h set DAC palette width
                BH = desired number of bits per primary color
            01h get DAC palette width
Return: AL = 4Fh if function supported
        AH = status
        BH = current number of bits per primary (06h = standard VGA)