Audio Routine

starfighter1314 · November 29, 2003

Hello All,

I am very new to hacking so please bear with my newbieness.

I have a new audio routine that I really want to test, but I am running into major difficulties implementing it. I want to hack an existing game with it, but whenever I do this, I get an error when assembling with DASM. So far, I have tried it with Combat, Adventure, and Home Run (I believe they are all 2K games which may be part of the difficulty). I got the source code for all of these from the web, except for Home Run which I had to use Distella for. When I run DASM after inserting the code, I get the error "Origin Reverse-indexed" when using Combat source code. For Adventure and Home Run, it assembles, but Stella won't run it properly (black screen). Maybe these games are optimized such that no more code can be added??

Anyway, if anyone can point me to some source code for any 1 player game that is reasonably documented (at least, the code surrounding collision detection during the game) that I can try my routine on I would really appreciate it. It can be a 2K or 4K game. If you can help me get this to work with Home Run, I would really, really appreciate it.

Thanks,

starfighter1314

PS I have already tried using source code from SCSIcide but could not get it to assemble using DASM (source not resolvable error message).

Thomas Jentzsch · November 29, 2003

Simply adding code won't work for various reasons.

1. Games may become larger than 2 or 4K then (reversed origin error).

2K games will increase to 4K then, so you must adjust the start vectors at the very end of the code. They must be at the end of the ROM space.

If 4K become too large, you would have to add bankswitching etc. which is almost impossible for a hacker.

2. The disassemblies might have missed some pointers, so when you insert some code, the hardcoded unrecognized pointers will not point at the correct spot anymore. And if you ony used DiStella this will happen almost always.

3. SCSIcide looks like a perfect candidate for the hack you are trying to do. IIRC there still is space left and all pointers etc. should be correct when using the original sourcecode.

Nukey Shay · November 29, 2003

...or how about that optimised Adventure code? That one has a lot of Rom space freed up already so you can experiment adding in your own routines to the existing game :idea: