Mr.Do Save High Score & Screen Flip
Here's the scoop on making Mr.Do save it's high-score
table, and in addition FLIP the screen ! I just put this page together quickly after I
finished hacking the ROMs, so it doesnt look the pretiest in the world, but anyway here's
how to do it...
Getting Mr.DO to save the high-score table was much easier than Galaga, for a start the board already uses 2k x 8 Static RAMs, so you can just replace the HM6116's, located at H4, with the Dallas battery backed parts. The only downside here was on my board, and at least 4 others I've checked, the RAMs were not socketed, so a little soldering needs to be performed.
The second step is the modified program ROM, this will stop the normal power on from clearing the high-score table and re-initializing it with the default values, however when the game goes into test mode then the high score table is erased, that seemed fair.
The second BIG thing was not high-score related, the monitor in Mr.Do is inverted, so running it in one of my standard cabinets, the screen is the wrong way up ! Very annoying, the game does not support a flip screen via a DIP switch, so I had to modify the program code to support flip screen. To do this I replaced the DIP switch for "rack advance" with a flip screen function, set the switch 'ON' the screen will be inverted.
I'm going to have a look at getting the between level, animations to move in the correct directions with the flip enabled, this doesnt distract from game play but would be nice to make the flip upgrade perfect.
If you dont use the flip feature then everything on the board, apart from rack advance, works as normal.
Two of the game program ROMs have been modified, you will
need to replace these to implement save hi-score and screen flip, the ROMs are 2764, or
27C64, these are 8k x 8 EPROMs.
You will need, 1 x 24pin socket, 2 x 2764 EPROMs, 1 x
DS1220AB static RAM -there's an alternative SGS Thompson part M48Z02 which should also
work. This is a 2k x 8 battery backed static RAM.
Skips steps 1 & 2 for just the flip screen.