Int 10 Fn 12  - Cirrus Logic BIOS - Get Video Mode Availability            [V]

   AH = 12h
   BL = A0h
   AL = video mode number (00h-7Fh)

Return: AH bit 0: video mode supported
   BX = offset of BIOS subroutine to fixup standard video parameters
       (call subroutine with DS:SI and ES:DI as returned by this call)
   DS:SI -> standard video parameters or FFFFh:FFFFh
   ES:DI -> supplemental video parameters or FFFFh:FFFFh

See Also: AH=00h,AH=12h/BL=9Ah,AH=12h/BL=A1h