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2F1605

Category: MS Windows
Flags: callout or callback (usually hooked rather than called)

INT 2F - MS Windows - WINDOWS ENHANCED MODE & 286 DOSX INIT BROADCAST

	AX = 1605h
	ES:BX = 0000h:0000h
	DS:SI = 0000h:0000h
	CX = 0000h
	DX = flags
	    bit 0 = 0 if Windows enhanced-mode initialization
	    bit 0 = 1 if Microsoft 286 DOS extender initialization
	    bits 1-15 reserved (undefined)
	DI = version number (major in upper byte, minor in lower)
Return: CX = 0000h if okay for Windows to load
	CX = FFFFh (other registers unchanged) if Windows 3.0 in standard mode
	CX <> 0 if Windows should not load
	ES:BX -> startup info structure (see #02631)
	DS:SI -> virtual86 mode enable/disable callback or 0000h:0000h
	      (see #02634)
Notes:	the Windows enhanced mode loader and Microsoft 286 DOS extender will
	  broadcast an INT 2F/AX=1605h call when initializing.	Any DOS device
	  driver or TSR can watch for this broadcast and return the appropriate
	  values.  If the driver or TSR returns CX <> 0, it is also its
	  responsibility to display an error message (however, Windows95 is
	  reported to load regardless of the returned CX).
	each handler must first chain to the prior INT 2F handler with
	  registers unchanged before processing the call
	if the handler requires local data on a per-VM basis, it must store the
	  returned ES:BX in the "next" field of a startup info structure and
	  return a pointer to that structure in ES:BX
	a single TSR may set the V86 mode enable/disable callback; if DS:SI is
	  already nonzero, the TSR must fail the initialization by setting CX
	  nonzero
	MSD checks for Windows 3.0 running in standard mode by testing whether
	  CX=FFFFh and other registers are unchanged on return
	Novell DOS v7.0 (Update 8 - Update 11) TASKMGR in multitasking mode
	  uses this broadcast, even if TASKMGR.INI sets WinPresent= to OFF
	Microsoft's EMM386.EXE for DOS 5+ when installed with the NOEMS option
	  changes its driver name from EMMQXXX0 to EMMXXXX0 while Windows is
	  active
SeeAlso: AX=1606h,AX=1608h,AX=4B05h


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  Copyright 2000   by Ralf Brown     Updated Jul 2000