PORTIBM PC Portable (uses same BIOS as XT) 03B0-03BF - 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.  (Monochrome Display Adapter based on 6845)

03B0  -W  same as 03B4
03B1  RW  same as 03B5
03B2  -W  same as 03B4
03B3  RW  same as 03B5
03B4  -W  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. CRT index register	 (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./mono 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./mono VGAVideo Graphics Array(Video Graphics Array) The video adapter introduced with the IBMInternational Busiuness Machines PS/2IBM PS/2, any model series of computers.)
		selects which register (0-11h) is to be accessed through 03B5h
		Note: this port is read/write on some VGAs
		bit7-6: (VGAVideo Graphics Array(Video Graphics Array) The video adapter introduced with the IBMInternational Busiuness Machines PS/2IBM PS/2, any model series of computers.) reserved (0)
		bit5  : (VGAVideo Graphics Array(Video Graphics Array) The video adapter introduced with the IBMInternational Busiuness Machines PS/2IBM PS/2, any model series of computers.) reserved for testing (0)
		bit4-0: selects which register is to be accessed through 03B5h
03B5  RW  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. CRT data register	 (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./mono 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./mono VGAVideo Graphics Array(Video Graphics Array) The video adapter introduced with the IBMInternational Busiuness Machines PS/2IBM PS/2, any model series of computers.) (see #P0654,#P0708)
		selected by PORTIBM PC Portable (uses same BIOS as XT) 03B4h. registers 0C-0F may be read
		Color adapters are at 3D4/3D5, but are mentioned here for
		  better overview.
		There are differences in names and some bits functionality
		  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., VGAVideo Graphics Array(Video Graphics Array) The video adapter introduced with the IBMInternational Busiuness Machines PS/2IBM PS/2, any model series of computers. in their native modes, but clones in their
		  emulation modes emulate the original 6845 at bit level. The
		  default values are for 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., 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. only, if not otherwise
		  mentioned.
03B6  -W  same as 03B4h
03B7  RW  same as 03B5h
03B8  rW  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. mode control register (see #P0655)
03B9  ?W  reserved for color select register on color adapter
03B9  -W  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.: set lightpen flipflop (value written is ignored)
		cannot be found on native mono 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., mono VGAVideo Graphics Array(Video Graphics Array) The video adapter introduced with the IBMInternational Busiuness Machines PS/2IBM PS/2, any model series of computers. (without
		  translation ROM(Read-Only Memory) A memory for program storage which may not be changed by the program as it runs.)
03BA  R-  CRT status register (see #P0656)
	    (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./VGAVideo Graphics Array(Video Graphics Array) The video adapter introduced with the IBMInternational Busiuness Machines PS/2IBM PS/2, any model series of computers.) input status 1 register
03BA  -W  (mono 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./mono VGAVideo Graphics Array(Video Graphics Array) The video adapter introduced with the IBMInternational Busiuness Machines PS/2IBM PS/2, any model series of computers.) feature control register
	    (see PORTIBM PC Portable (uses same BIOS as XT) 03DAh-W for details; VGAVideo Graphics Array(Video Graphics Array) The video adapter introduced with the IBMInternational Busiuness Machines PS/2IBM PS/2, any model series of computers., see PORTIBM PC Portable (uses same BIOS as XT) 03CAh-R)
03BB  -W  light pen strobe reset (on any value)


(Table P0654)
Values for mono video adapter CRT data register index:
				  defaults:    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.	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.   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.   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.	  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.
						 text  graph text1 text2 graph
						   7  720x348  1     3	  5,6
 00h	horizontal total			  61h	35h   38h   71h	  38h
	      ET4000: in VGAVideo Graphics Array(Video Graphics Array) The video adapter introduced with the IBMInternational Busiuness Machines PS/2IBM PS/2, any model series of computers. mode scanlines-5
		      in 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. mode scanlines-2
 01h	horizontal displayed			  50h	2Dh   28h   50h	  28h
	      horizontal display end-1 (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.,VGAVideo Graphics Array(Video Graphics Array) The video adapter introduced with the IBMInternational Busiuness Machines PS/2IBM PS/2, any model series of computers.)
 02h	horizontal sync position		  52h	2Eh   2Dh 5Ah/5Ch 2Dh
 03h	sync pulse width			  0Fh 07h/0Fh 0Ah   0Ah	  0Ah
	       bit7-4 vsync, bit3-0 hsync
	      end horizontal blanking (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.,VGAVideo Graphics Array(Video Graphics Array) The video adapter introduced with the IBMInternational Busiuness Machines PS/2IBM PS/2, any model series of computers.)
	       VGAVideo Graphics Array(Video Graphics Array) The video adapter introduced with the IBMInternational Busiuness Machines PS/2IBM PS/2, any model series of computers.    : bit7=1	  : enable read access to regs
				    10h, 11h (otherwise 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
				    may show lightpen values)
	       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.,VGAVideo Graphics Array(Video Graphics Array) The video adapter introduced with the IBMInternational Busiuness Machines PS/2IBM PS/2, any model series of computers.: bit6-5=0-3: display enable skew control
			bit4-0	  : end blanking
 04h	vertical total (vcycle-1)		  19h	5Bh   1Fh   1Fh	  7Fh
	       bit7 only used on MCGAMulti-Color Graphics Array(Multi-Color Graphics Array) The low-end color adapter offered in IBMInternational Busiuness Machines's early PS/2IBM PS/2, any model series machines.
	      start horizontal retrace (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., VGAVideo Graphics Array(Video Graphics Array) The video adapter introduced with the IBMInternational Busiuness Machines PS/2IBM PS/2, any model series of computers.)
	      Genoa SuperEGA only???:
	       bit7  : start at odd memory address
	       bit6-5: horizontal sync skew
	       bit4-0: start retrace+ retrace width
 05h	vertical total adjust			  06h	02h   06h   06h	  06h
	       bit7-5 only used on MCGAMulti-Color Graphics Array(Multi-Color Graphics Array) The low-end color adapter offered in IBMInternational Busiuness Machines's early PS/2IBM PS/2, any model series machines.
	      end horizontal retrace (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., VGAVideo Graphics Array(Video Graphics Array) The video adapter introduced with the IBMInternational Busiuness Machines PS/2IBM PS/2, any model series of computers.)
	       bit7  : (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.) start at odd memory address
		       (VGAVideo Graphics Array(Video Graphics Array) The video adapter introduced with the IBMInternational Busiuness Machines PS/2IBM PS/2, any model series of computers.) bit5 of end horizontal retrace
	       bit6-5: horizontal sync skew
	       bit4-0: end horizontal retrace
 06h	vertical displayed			  19h	57h   19h   19h	  64h
	       bit7 only used on MCGAMulti-Color Graphics Array(Multi-Color Graphics Array) The low-end color adapter offered in IBMInternational Busiuness Machines's early PS/2IBM PS/2, any model series machines.
	      (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.) vertical total-1
	      (VGAVideo Graphics Array(Video Graphics Array) The video adapter introduced with the IBMInternational Busiuness Machines PS/2IBM PS/2, any model series of computers.) vertical total-2
 07h	vertical sync pulse width-1		  19h	57h   1Ch   1Ch 70h/66h
	       bit7  only used on MCGAMulti-Color Graphics Array(Multi-Color Graphics Array) The low-end color adapter offered in IBMInternational Busiuness Machines's early PS/2IBM PS/2, any model series machines.
	      controller overflow (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.,VGAVideo Graphics Array(Video Graphics Array) The video adapter introduced with the IBMInternational Busiuness Machines PS/2IBM PS/2, any model series of computers.)
	       bit7: (VGAVideo Graphics Array(Video Graphics Array) The video adapter introduced with the IBMInternational Busiuness Machines PS/2IBM PS/2, any model series of computers.) bit9 of start vertical retrace (10h)
	       bit6: (VGAVideo Graphics Array(Video Graphics Array) The video adapter introduced with the IBMInternational Busiuness Machines PS/2IBM PS/2, any model series of computers.) bit9 of vertical display end (12h)
	       bit5: (VGAVideo Graphics Array(Video Graphics Array) The video adapter introduced with the IBMInternational Busiuness Machines PS/2IBM PS/2, any model series of computers.) bit9 of vertical total (06h)
		     (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.) bit5 of cursor-position (0Ah)
	       bit4: bit8 of line compare (18h)
	       bit3: bit8 of start vertical blanking (15h)
	       bit2: bit8 of vertical retrace start (10h)
	       bit1: bit8 of vertical display end (12h)
	       bit0: bit8 of vertical total (06h)
 08h	interlace mode (not MCGAMulti-Color Graphics Array(Multi-Color Graphics Array) The low-end color adapter offered in IBMInternational Busiuness Machines's early PS/2IBM PS/2, any model series machines.)		  02h	02h   02h   02h	  02h
	       bit7-2: reserved
	       bit1  : delay
	       bit0=1: interlace on
	      preset row scan (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., VGAVideo Graphics Array(Video Graphics Array) The video adapter introduced with the IBMInternational Busiuness Machines PS/2IBM PS/2, any model series of computers.)
	       bit7  : reserved
	       bit6-5: (VGAVideo Graphics Array(Video Graphics Array) The video adapter introduced with the IBMInternational Busiuness Machines PS/2IBM PS/2, any model series of computers.) byte panning (low-order bits of display start addr
		  in odd/even and quad modes
	       bit4-0: start row scan after retrace
 09h	maximum scan lines			  0Dh	03h   07h   07h	  01h
	       bit7  : (VGAVideo Graphics Array(Video Graphics Array) The video adapter introduced with the IBMInternational Busiuness Machines PS/2IBM PS/2, any model series of computers.) double scan active
	       bit6  : (VGAVideo Graphics Array(Video Graphics Array) The video adapter introduced with the IBMInternational Busiuness Machines PS/2IBM PS/2, any model series of computers.) bit9 of line compare (18h)
	       bit5  : (VGAVideo Graphics Array(Video Graphics Array) The video adapter introduced with the IBMInternational Busiuness Machines PS/2IBM PS/2, any model series of computers.) bit9 of start vertical blanking (15h)
	       bit4-0: maximum scan line 00..31 (height-1)
 0Ah	cursor start				  0Bh	00h   06h   06h 06h/00h
	       bit7  : reserved
	       bit6-5: original 6845: cursor on/off, blink interval
		       (not on all adapters, as original 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., 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. have
		       extra circuitrity to avoid this!!)
	       bit6-5: native 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.: not used
	       bit6  : (VGAVideo Graphics Array(Video Graphics Array) The video adapter introduced with the IBMInternational Busiuness Machines PS/2IBM PS/2, any model series of computers.) not used
	       bit5=0: (VGAVideo Graphics Array(Video Graphics Array) The video adapter introduced with the IBMInternational Busiuness Machines PS/2IBM PS/2, any model series of computers.) cursor on
	       bit4-0: first cursor scanline
 0Bh	cursor end				  0Ch	00h   07h   07h 07h/00h
	       bit7  : reserved
	       bit6-5: 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., VGAVideo Graphics Array(Video Graphics Array) The video adapter introduced with the IBMInternational Busiuness Machines PS/2IBM PS/2, any model series of computers.: cursor skew control
	       bit4-0: end cursor row
 0Ch RW	start address high			  00h	00h   00h   00h	  00h
	       bit7-6 not used by original 6845 (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.,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.)
 0Dh RW	start address low			  00h	00h   00h   00h	  00h
 0Eh RW	cursor location high			  00h	00h   00h   00h	  00h
	       bit7-4 not used by original 6845 (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.,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.)
	       bit5-4 reserved on MCGAMulti-Color Graphics Array(Multi-Color Graphics Array) The low-end color adapter offered in IBMInternational Busiuness Machines's early PS/2IBM PS/2, any model series machines.
 0Fh RW cursor location low			  00h	00h   00h   00h	  00h
 10h R-	light pen high (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./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./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. only, some 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., few 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 emulation, not with ET4000)
 10h R- MCGAMulti-Color Graphics Array(Multi-Color Graphics Array) The low-end color adapter offered in IBMInternational Busiuness Machines's early PS/2IBM PS/2, any model series machines. at 3D5h only: mode control status register (see #P0711)
 11h R- light pen low (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./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./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. only, some 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., few 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 emulation, not with ET4000)
 14h -W HGC+,InColor: xMode register
 15h -W HGC+,InColor: underscore register
 16h -W HGC+,InColor: overstrike register
 17h -W	InColor: exception register
 18h -W	InColor: plane mask register
 19h -W	InColor: read/write control register
 1Ah -W	InColor: read/write color register
 1Bh -W	InColor: Latch Protect register
 1Ch RW	InColor: palette register
Notes:	registers 10h and 11h have varying uses on VGAVideo Graphics Array(Video Graphics Array) The video adapter introduced with the IBMInternational Busiuness Machines PS/2IBM PS/2, any model series of computers. (see #P0708) and
	  MCGAMulti-Color Graphics Array(Multi-Color Graphics Array) The low-end color adapter offered in IBMInternational Busiuness Machines's early PS/2IBM PS/2, any model series machines. (see #P0710)
	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., 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.: 6845 registers 00h-0Dh are write only, 0Eh, 0Fh
	       are r/w, and 10h-11h are read only.
	       The alternative initial defaults may be used
	       sometimes on modern adapters.
	HGC+(RamFont): as with 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., but 3 additional registers for font control
	emulations   : more registers may be r/w, but most often it's the
	       same as with native 6845.
	MCGAMulti-Color Graphics Array(Multi-Color Graphics Array) The low-end color adapter offered in IBMInternational Busiuness Machines's early PS/2IBM PS/2, any model series machines. (CGA+)  : Though this is a mixture of 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. 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., most
	       registers are same as with 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., but with some
	       enhancements and incompatibilities to 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., VGAVideo Graphics Array(Video Graphics Array) The video adapter introduced with the IBMInternational Busiuness Machines PS/2IBM PS/2, any model series of computers..
	native 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.   : registers 00h-0Bh are write only, 0Ch-0Fh are
	       r/w, 10h-11h are read/write, 12h-18h are write
	       only. More regs may be r/w on enhanced clones.
	GenoaSuperEGA: adapter with chips SEQCRT GN006001 and GRAT
	       GN006002, e.g. c't Super-EGA adapter. Is 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.
	       clone with up to 800x600 and full 6845 emulation.
	native VGAVideo Graphics Array(Video Graphics Array) The video adapter introduced with the IBMInternational Busiuness Machines PS/2IBM PS/2, any model series of computers.   : all registers 00-18h are r/w, but 00h-07h are
	       write-locked if bit7 in 11h is set.
	ET4000	     : same as VGAVideo Graphics Array(Video Graphics Array) The video adapter introduced with the IBMInternational Busiuness Machines PS/2IBM PS/2, any model series of computers., but with additional r/w registers
	       32h-37h, protected by 'key' except 33h, 35h
	       (see 3BFh for details). 35h is protected by
	       bit7 in 11h. The 'key' must be issued at least
	       after each power on or synchronous reset.
SeeAlso: #P0708,#P0710,#P0655,#P0656,#P0710


Bitfields for mono video adapter mode control register:
Bit(s)	Description	(Table P0655)
 7 not used by 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., page number on 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.
 6	not used
 6  R-O	(mono ET4000 only) report status of bit 1 (enable 2nd page) of
	  Hercules compatibility register (PORTIBM PC Portable (uses same BIOS as XT) 03BFh)
 5	enable blink (0 = intense background, 1 = blink)
 4	not used
 3	video enable
 2	not used
 1	(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.) not used
	(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 enable
	the 6845 has to be reprogrammed completely, if this bit is
	  changed, otherwise the TTL-monitor may be damaged by wrong
	  sync impulses!
 0	high resolution mode (always set on 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.)
---mono ET4000 only, W-O ---
 7-0	=A0h: second part of 'key', see Hercules compatibility register
	  (PORTIBM PC Portable (uses same BIOS as XT) 03BFh) for details
Note:	this port might be completely or partially readable on very few 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. clones or emulations (e.g. Genoa SuperEGA), but not with the
	  majority of original and clone chips.	 It cannot be found on
	  native mono 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., mono VGAVideo Graphics Array(Video Graphics Array) The video adapter introduced with the IBMInternational Busiuness Machines PS/2IBM PS/2, any model series of computers., but on most clones, where it is usually
	  R/W.
SeeAlso: #P0654,#P0656


Bitfields for mono video adapter CRT status register:
Bit(s)	Description	(Table P0656)
 7	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.: vertical sync pulse in progress
 6-4	adapter identification
	(MSD says) if bit 7 changes within 8000h reads then
	    =000 adapter is Hercules or compatible
	    =001 adapter is Hercules+
	    =101 adapter is Hercules InColor
	    else: adapter is unknown
 6-4	=111 on 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. and some 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. clones
 5-4	(mono 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., mono ET4000) diagnose video display feedback
	select from color plane enable
 3	(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.) pixel stream (0=currently black, 1=currently white)
	(mono 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., mono VGAVideo Graphics Array(Video Graphics Array) The video adapter introduced with the IBMInternational Busiuness Machines PS/2IBM PS/2, any model series of computers.) vertical retrace in progress
 2-1	(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.) reserved
 2	(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., mono 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.) lightpen flipflop set
	(mono ET4000) reserved (0)
 1	(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.) lightpen input stream (if set, current value to get from
	  PORTIBM PC Portable (uses same BIOS as XT) 03B5h registers 10h-11h)
	(mono ET4000) reserved (0)
 0	horizontal drive enabled
SeeAlso: #P0654,#P0655


Bitfields for 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.,VGAVideo Graphics Array(Video Graphics Array) The video adapter introduced with the IBMInternational Busiuness Machines PS/2IBM PS/2, any model series of computers. mode control register:
Bit(s)	Description	(Table P0657)
 7	0=CRTC reset and stop, 1=resume reset
 6	0=word-mode, 1=byte-mode (VGAVideo Graphics Array(Video Graphics Array) The video adapter introduced with the IBMInternational Busiuness Machines PS/2IBM PS/2, any model series of computers.: see 14h, bit6)
 5	0=14bit, 1=16bit address wrap
 4	(native VGAVideo Graphics Array(Video Graphics Array) The video adapter introduced with the IBMInternational Busiuness Machines PS/2IBM PS/2, any model series of computers. only) reserved (0)
 4	(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 most 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) output control
	0: video driver active
	1: video driver not active
 3	linear address counter clock (0 = standard, 1 = clock/2)
	(VGAVideo Graphics Array(Video Graphics Array) The video adapter introduced with the IBMInternational Busiuness Machines PS/2IBM PS/2, any model series of computers.: see register 14h, bit 5)
 2	horizontal retrace clock (0 = standard, 1 = clock/2)
 1	row scan counter
	0: address bit 14 = scan bit 1
	1: address bit 14 not altered
 0	6845 compatibility mode
	0: address bit 13 = scan bit 0 (as with 6845)
	1: address bit 13 not altered
SeeAlso: #P0654