INT 2F U - DOS 4+ XMA2EMS.SYS extension internal - INSTALLATION CHECK 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. SeeAlso: AH=1Bh"FRAME INFO"