RBIL61 - PORT 03BF - Hercules configuration switch register

PORTIBM PC Portable (uses same BIOS as XT) 03BF - Hercules configuration switch register
Note:	can also be found on EGAEnhanced Graphics Adapter(Enhanced Graphics Adapter) IBMInternational Busiuness Machines's second color video board for the IBMInternational Busiuness Machines PCIBM PC family, capable of a maximum resolution of 640x350 pixels in 16 simultaneous colors of a total of 64 possible colors. and VGAVideo Graphics Array(Video Graphics Array) The video adapter introduced with the IBMInternational Busiuness Machines PS/2IBM PS/2, any model series of computers. clones in Hercules emulation

03BF  -W  configuration switch register (see #P0660)
03BF  -W  (ET4000) Hercules compatibility register (see #P0661)
03BF  RW  (Genoa SuperEGA) miscellaneous register
	Note: only available in MDA(Monochrome Display Adapter) A text-only video adapter introduced together with the original IBMInternational Busiuness Machines PCIBM PC.  See also CGAColor Graphics Adapter, HGC., HGC(Hercules Graphics Card) A monochrome video adapter capable of 720x352 monochrome graphics.	 The HGC was the first non-IBM video adapter for the IBMInternational Busiuness Machines PCIBM PC.	 See also CGAColor Graphics Adapter, MDA., and CGAColor Graphics Adapter(Color/Graphics Adapter) One of the two video display boards introduced together with the original IBMInternational Busiuness Machines PCIBM PC.  See also HGC, MDA. emulation; should be
	  compatible with Hercules configuration register, but may contain
	  additional features


Bitfields for Hercules configuration switch register:
Bit(s)	Description	(Table P0660)
 7-2	reserved
 1	=0  disables upper 32K of graphics mode buffer
	=1  enables upper 32K of graphics mode buffer
 0	=0  prevents graphics mode
	=1  allows graphics mode
SeeAlso: #P0661


Bitfields for ET4000 compatibility register:
Bit(s)	Description	(Table P0661)
 1	=0 disables upper 32K of graphics mode buffer
	=1 enables upper 32K of graphics mode buffer
 0	reserved (not needed for HGC(Hercules Graphics Card) A monochrome video adapter capable of 720x352 monochrome graphics.	 The HGC was the first non-IBM video adapter for the IBMInternational Busiuness Machines PCIBM PC.	 See also CGAColor Graphics Adapter, MDA. graphics)
 7-0	=03h: first part of 'key' for access to some extra
	     ET4000 regs. To issue the 'key', the following
	     code must be executed:
	      MOV DX, 3BFh
	      MOV AL, 3
	      OUT DX, AL
	      MOV DX, 3D8h  (3B8h in mono mode)
	      MOV AL, 0A0h
	      OUT DX, AL
SeeAlso: #P0660