Int 10 Fn 4F08  - Vesa Supervga Bios V1.2+ - Get/set Dac Palette Control   [V]

   AX = 4F08h
   BL = subfunction
       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
       00h successful
       01h failed
   BH = current number of bits per primary (06h = standard VGA)