Int 21 Fn 64  U - OS/2 V2.1+ Virtual DOS Machine - Get Winos2 Call Gate A  [O]

   AH = 64h
   DX = 0007h (function number)
   CX = 636Ch (magic value, "cl")
   BX = 0000h (indicates special request)

Return: AX = call gate address

Notes: if CX is not 636Ch on entry, INT 21/AH=6Ch is invoked, because a bug
     in OS/2 1.x FAPI erroneously called AH=64h instead of AH=6Ch
   used by WinOS2 to make direct calls to OS2KRNL, bypassing the overhead
     of DOSKRNL