Int 21 Fn 4321  - Q87, Q387 - Disable Emulator                             [u]

   AX = 4321h
   BX = 0002h
   EAX = 87654321h (entire EAX value is required, not just AX)
Desc:  disable the emulator by clearing the CPU MSW's EM bit and updating
     the BIOS equipment list

Note:  this function is available only in virtual-86 mode in older versions;
     newer versions also provide it in MS Windows 16- and 32-bit protected
     mode

See Also: AX=4321h/BX=0000h,AX=4321h/BX=0001h