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Activision Tennis disassembly


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Ok, first off I am NOT a 2600 programmer.   But I have used some of @DEBRO's to port some games to the 8-bit machines.  His disassembles are great, so thanks!


I've (badly) attempted to use his style (sort-of) in disassembling this one.  It's a mess, it's incomplete, I'm sure many labels are wrong, I don't really know what the heck I'm doing, basically. 


However, at least some of it IS right, and it assembles back into the original ROM, same MD5 hash, etc...  I'm posting this for posterity, maybe someone will find it useful, or want to help with it, or point out my mistakes, etc.  I haven't even attempted to get into the AI or gameplay aspects, but some fair amount is labeled and commented.


Not asking for anything here, really.  Just sharing this thing as-is, warts and all...  Don't be too hard on me, I've never tried a from-scratch 2600 disassembly like this.



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A few comments on this one.  I started doing this with the intention of porting it to the 8-bit machines, as I've done with a few others.  But that's probably not going to happen.  This thing is coded weird!  It uses lots of 2600-specific stuff, and the coordinate system seems based on a decrementing scanline counter, instead of any kind of "normal" X/Y stuff.  Also lots of overlapping data/things, probably to save space.  But it makes it quite confusing.  It looks like it took a lot of effort to get it all in under 2K.


And yet, with lots of RAM locations free ($D6 and above, I think) he saves some things on the stack, pha/pla...  Maybe to get the cycle counts to work, who knows.  I thought this would be an easy one to port to 8-bit, but I think I've changed my mind.


So, end result, I have no compelling reason to work on it any further.  But I guess, if someone wanted to it could be turned into a 4K game with added features...  

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