Int 10 Fn 12  - Video - Alternate Function Select (vga) - Select Vertical  [V]

   AH = 12h
   BL = 30h
   AL = vertical resolution
        00h 200 scan lines
        01h 350 scan lines
        02h 400 scan lines

Return: AL = 12h if function supported
Desc:  specify the number of scan lines used to display text modes

Note:  the specified resolution will take effect on the next mode set

See Also: AH=00h