Int 21 Fn FF  UP - Rational Systems Dos/4gw - ???                          [E]

   AH = FFh
   DH = 0Eh

Return: DX:AX -> XBRK structure (see #0432 at INT 15/AX=BF02h)
   BX = ???
   CX = ???

See Also: INT 15/AX=BF02h