Edit, Save, and Use Hex Files

[DavidDownUnder]

I recently came across a "trainer" file online for one of my all-time Atari favourites, Spelunker. The file seems to do its magic of giving 255 lives by writing $FF to address $CB. I'd like to use this on the emulator on my handheld device (PSP) when travelling, but that emulator does not seem to have a way to load these trainer files, so I was wondering about disassembling the image (yes, I own the Atari disk, LOL) and changing the appropriate bytes. Tried this using Omnivore but on launching Altirra it doesn't do the trick. Any guidance? Sorry, but I last had assembly language programming in engineering school many(!) years ago, so I remember just enough to be dangerous! 

Edited June 5, 2020 by DavidDownUnder

[Roydea6]

If this disk is the one from Borderbund.  It would be easier to just download the Spelunker file already trained or hex editied. and use that one in your emulator.

 

Spelunker[Title & Intro].ATR

 

This will need to be edited for the proper codes.

Edited June 5, 2020 by Roydea6
added the file.

[DavidDownUnder]

Thanks, mate. I have the image already just not sure how to save the changes for use on the device where loading trainer files does not seem doable. I can edit the file with a hex editor but do not know how to save it as a usable, hacked image.

[Rybags]

The animated intro Spelunker is encrypted.  Not sure about the other one.

In the case of most games they won't be encrypted.

 

XEX games (file) will have start/end address for segments in the file describing where to load/run etc.  If you first use a utility to list the segments you can work out the offset in the file for a given address assuming it's part of the loading.

If you have a cheat where you're constantly forcing a value to a location then chances are you can't reproduce it on disk.

You want a cheat where you're changing the initial value that gets loaded into the lives working variable.

For an ATR the load address will be in the first 6 bytes of data but many full disk games will load a few sectors then handover to a loader that does the rest.

 

Probably the easiest method for ATR - and again you'd want to be changing the program and not some work variable - would be to grab several bytes before/after the patched one then do a search on that string of bytes.  Assuming you only find it once that should be the location that you need to change.

 

An alternate that should work with Spelunker assuming you keep plugging $FF into $CB is a Ram based OS with code inserted to do that patch.

[DavidDownUnder]

Thanks again, mate. Sounds like I need to scour the Internet and find an already-hacked version. I actually finished this game on my 800XL many years ago, no way I could do it now without cheating! 

[Rybags]

Spelunker is pretty easy to finish once you know a few of the tricks.

#1 is conserve the air, which becomes most important when you're in the Shaft level since there's lots of waiting for the water to go up & down to carry you across.

#2 probably dealing with the ghosts.  Often best to be strategic, sometimes the best way is to kill them at the last possible moment.

#3 is learning to jump around on the moving ladders without falling and dying.

 

I was going to propose some time back a decryption project to get the game plainly viewable, next thing after that might be some rev-engineering with the aim to make new maps.

Though the game is simple enough that a workalike engine could probably be done with not too much effort.

[Roydea6]

1 hour ago, DavidDownUnder said:

find an already-hacked version.

Spelunker Infinite Lives Micro Graphic Image(1983).atr

 

 

[DavidDownUnder]

WOW, thanks mate!