This is what Venus forgot to tell you about. The format (or even existance!)
of MGH-tag files. Tag files are available to you for 2 reasons. The first is
to allow you to run a 'special' game with some 'extra' code. The best example
is the first file that I knew of for Street Fighter 2 Turbo. This was a
2048 byte .MGH file that showed the title of the game next to the directory
entry, and allowed the MGH to load the game properly from 4 parts. (which the
MGH will not normally do). The second is probably the text which appears on
the screen. This is a nice touch that Venus didn't mention. I would guess that
the real reason behind this is that it allows Asian users to add in the games
title in proper Chinese characters (which the MGH does NOT have in ROM).
An MGH tag file should have the SAME name as the matching file, with the
file-extension '.MGH'.

SNES .MGH format:
	dc.b	'MGH',$1a
	dc.b	$0F	;colour 1&2 - explained below
	dc.b	$FF	;colour 3&4...
	dc.b	0
	dc.b	0	;0-means name ONLY, $C0 means CONTROL file
	dc.b	0,0,0,0,0,0,0
	dc.b	'Title of game  ',$FF	;15 character string to display

bytes 32-512 are a 'graphic' that you can create if you'd rather display this
then text. This is useful to create a Chinese name for the game.

This is in essance what the header of the SNES .MGH file looks like. The .MGH
file is loaded at address $E00. With the control byte set, the MGH will look for
executable code at address $1000. The colour bytes are only used for the
graphic (if present) and NOT for the ASCII string that you use.


The Genesis side appears to REQUIRE that you 'draw' to the screen. The graphic
that you use will appear in the box at the bottom. You have 2 lines of 15,
8x8 cells available to you. A Genesis .MGH file should be 512 bytes long.

For example: If you wanted the letter 'A' to appear in the first position, and
you defined the cell as the 8 bytes:$18,$24,$42,$42,$7E,$42,$42,0, then you
create an .MGH file with the format:

	dc.b	'MGH',0		;$1a is not needed on the Genesis side...
	dc.b	$0F,$23		;colour1=blue (background)
				;colour2=white
				;colour3=green
				;colour4=light green
	dcb.b	26,0		;26 zeros follow...
byte32	dc.b	$18,$24,$42,$42,$7E,$42,$42,0,0,0,0,0,0,0,0,0
bytes40-512 should be 0's

since there are 2 bit-planes you will see the letter 'A' in white.
For green:		dc.b	0,0,0,0,0,0,0,0,$18,$24,$42,$42,$7E,$42,$42,0
For light green:	dc.b	$18,$24,$42,$42,$7E,$42,$42,0
			dc.b	$18,$24,$42,$42,$7E,$42,$42,0
or you can of course 'stripe' and mix and match your colours as you like

The available colours are:
0=dark blue, 1=dark red, 2=green, 3=light green, 4=black, 5=purple,
6=light blue, 7=dark grey, 8=light grey, 9=red, 10=green, 11=yellow
12=light blue, 13=purple, 14=light blue, 15=white

I do not have access to a good Z-80 disassembler, and am NOT able to hack the
Genesis side of the MGH ROM's. I don't know if the control byte works the
same way on the Genesis side or not. The control byte can be useful on SNES. I
have successfully split an 8Mbit game into 2 4Mbit halves, and successfully 
loaded the game on the MGH at the PROPER addresses using an .MGH control file.
From what I have seen of the ROMs, a 'Software Extension' works in a similar
manner. (This is what the 'Execute' under Tools is for) I will be able in the
near future to write proper/useful software extensions for splitting/joining
files and anything else that appears useful. However the Mgh that I now use is
faulty, and will not allow me to upgrade the DOS in the machine, so I cannot
test these ideas.

It seems that there is no one out there who has taken an interest in
programming on the MGH. If you are interested and capable of creating useful
software on the MGH, I can be contacted on STampede BBS is Florida/USA
---------------------------------------------------------------------------
Atari users should be on the look-out for my MGH util which is nearing it's
first general release. My util will convert to and from: SNES-Game Doctor,
Super Magic Com (Wild card), and Pro Fighter formats. Genesis-Game Doctor,
Magic Drive, Binary. It also allows you to add and create IPS and Baseline
trainer patches (withOUT converting to SMC first!) Decode/Encode Game Genie/
Game Finger codes for SNES and Genesis (no GF on Genesis, but absolute are
useful for programmers) All file informations. Create/alter .MGH files.
Split/join files... All in a unique GEM interface, MultiTos complient.

Until then, get in touch! - ClockWork Orange/ICS

----------------------------------------------------------------------------
I'll include a couple of sample .MGH files in this archive for both machines
so you can see EXACTLY what I mean...

SFJOEMAC.MGH is for the SNES game 'Joe and Mac'
MDGNG.MGH is for the Genesis game Ghoul's and Ghosts

I am also including the Atari Tag-file program that I wrote awhile back. This
will create tag-files for SNES only... read the docs.
