Int 14 Fn F4FF  - Ibm/yale Ebios Serial I/o - Installation Check           [S]

   AX = F4FFh
   DX = port (00h-03h)

Return: CF clear if present
       AX = 0000h
   CF set if not present
       AX <> 0000h

See Also: AH=36h"ComShare",AH=F9h,AH=FCh