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

   AH = FFh
   DH = 00h
   DL = ??? (78h seen)

Return: CF clear
   EAX = 4734FFFFh (high word is byte-swapped "4G") if DOS/4G installed

Note:  Quarterdeck's DESQview/X X Toolkit library uses this call to determine
     whether the direct-mapped linear 4GB segment's selector is 34h or 38h

See Also: INT 21/AH=FFh/DH=00h"DOS/4GW"