Concatenating 2 16k ROMs into 1 32k

[CDS Games]

Just discovered how easy it was to combine ROMs into larger ones using concatenate in Unix (I'm on a Mac and don't have a running compiler--I do all my hacking right in Stella). Turned Combat into a 4k, then 8k bankswitched ROM and it ran great in Stella.

 

But I tried to do the same with a hack of Dark Chambers and though 8 banks show up, it won't run. Did the same thing I did with Combat: took the two 16k files, concatenated them, and then reset the ROM preferences in Stella to F4SC (32k Atari + ram)--Dark Chambers runs with SARA.

 

I have a feeling I'm missing something very basic, so any advice or help would be much appreciated.

[Wickeycolumbus]

It's possible that the game uses data that is present in the addresses of the additional hotspots that are used for F4 banking. When it is accessed in the game, it would trigger an unwanted bankswitch and probably crash.

[Omegamatrix]

The hotspots are different from 16 to 32k. You have to modify the game to run in Stella. Also how are you going between games. Dipswitch?

[CDS Games]

It's possible that the game uses data that is present in the addresses of the additional hotspots that are used for F4 banking. When it is accessed in the game, it would trigger an unwanted bankswitch and probably crash.

 

Ah...that makes sense. I will look into that.

[CDS Games]

The hotspots are different from 16 to 32k. You have to modify the game to run in Stella. Also how are you going between games. Dipswitch?

 

Ok I will dig back into the bankswitching tutorials and pore over the disassembly, see if I can uncover what is going on.

 

The idea was to switch back and forth within the game, with the switch points at the level transitions. So every odd level it runs in banks 1-4, then every even level it runs in banks 5-8.

[CDS Games]

Fantastic advice guys, both those suggestions did the trick. I changed all the bankswitching hotspots to work for F4 and zeroed out the relevant addresses.

 

This opens up a whole bunch of possibilities.

[Wickeycolumbus]

Fantastic advice guys, both those suggestions did the trick. I changed all the bankswitching hotspots to work for F4 and zeroed out the relevant addresses.

 

This opens up a whole bunch of possibilities.

 

 

Zeroing out the data won't help the issue that I mentioned if the game is still looking there for data. I think what Omega was talking about is that you need to make sure that hitting a certain hotspot will get you to the actual bank that the software expects. For example, making a 16K game out of an 8K one, you would have:

 
F8              F6         F4
 
                          $1FF4
                          $1FF5
           $1FF6          $1FF6
           $1FF7          $1FF7
$1FF8      $1FF8          $1FF8
$1FF9      $1FF9          $1FF9
                          $1FFA
                          $1FFB
 
 

So trying to run an 8K game that sits in the last 8K region will hop to the region in F8/F9 whenever a bankswitch is hit. In a multicart, you would probably just have switches that set the upper address and F8 bankswitching logic so you wouldn't have to hack the games to use the proper hot spots. If it's all the same game over again in the 32K, I don't see why it wouldn't just work. I'm not sure I understand the goal, are you planning on making a multicart? Or some type of cart that changes the game after a game over?

Edited November 14, 2015 by Wickeycolumbus

[CDS Games]

I probably explained it badly. What I meant by zeroing out was that although I corrected the bankswitching addresses from F6 to F4, there was an instruction in FFF4 and FFF5 that I had to move so those addresses would be clear. I checked to make sure the program knew to find those instructions at the new location so it all worked out.

 

Nope not planning on a multicart. The idea is simply that by having two parallel games I can have a greater variety of enemies, mazes, objects that just can't be fit into one. It's part of the Gauntlet port I'm working on here:

 

http://atariage.com/forums/topic/238273-dark-chambers-to-gauntlet-conversion/