Int 2F Fn 1B00  U - DOS 4+ Xma2ems.sys Extension Internal - Installation   [m]

   AX = 1B00h

Return: AL = FFh if installed

Note:  XMA2EMS.SYS extension is only installed if DOS has page frames to hide.
   This extension hooks onto INT 67/AH=58h and returns from that call data
     which excludes the physical pages being used by DOS.

See Also: AH=1Bh"FRAME INFO"