JOUST PAUSE MODIFICATION (WHITE/GREEN LABEL VERSION)  8/10/08 Ver 2.0

This hack gives previously unimplemented pause mode for Williams Robotron Arcade game.  It was designed to allow pausing during game play using the "1 player start" button.

History:

vER2:
Joust seems to use a totally different programming model from Robotron (the first williams mod) in that it lacks or doesnt use a character based printing routine; instead it blits a graphic of each character on the screen.  Well, at the very least it does not use ASCII strings, which makes it complicated to manually get characters on the screen.  

Joust also contains a little steaming nugget of code at 6AC7 that does a quick checksum on the one ROM that has any room to do mods when first starting a game.  If the checksum fails, it merely increments a value in page 0 that will corrupt execution later on in the game, in a seemingly random way.  So, byte DFF3 is used to reset the checksum to the correct value of A1.  I can't see it having any other purpose but to prevent changes by either the suits at Williams, or to would be bootleggers.

The silver lining is that ROM12 did not have to be reprogramed (where the checksums are located) so that a ROM error would not be triggered.  So while this mod was a pain in the ass to develop, its easy in that only 1 EPROM needs to be programmed.



Ver1:

Basic pause functionality using the 1Player start button.



Possible improvements:
1.  You tell me!




To use:

Burn replacement for ROM 10 (3006-22.10b), and install.

While in game, press 1P Start to toggle pause.


Downloaded from COINOPLOVE.COM