Help: Hex Editing Save States in Genesis Plus

anubis

I'm new to mac emulators and I could really use some help in trying to figure out how to hack into save states for genesis plus (for the matter - all mac emulator save states). I am trying to do the "the wacky adventures of rhys" hack for phantasy star 3 found on Hugues Johnson's website:

http://ps3.huguesjohnson.com/wacky.html

Any help in mac emulation would be greatly appreciated!

Squirrel

Here's the problem with savestates in regards to hacking like that webpage suggests: each emulator has their own way of making savestates. They are all completely incompatible with one another. Sometimes the Mac version of an emulator will have a different savestate format than the Windows version.

The webpage you linked us to REQUIRES you to use Genecyst (which in turn requires you to use Windows). There's no way around it.

Now, I'm not going to say it's impossible to do this using Genesis Plus. It's just highly unlikely for someone to figure this out because you need two pieces of information that I don't think anybody knows:
1 - what offset in savestates for Genecyst does the RAM start?
2 - what offset in savestates for Genesis Plus does the RAM start?
(I'm assuming the hacking the webpage is telling you to do is for the RAM.)

Even if you had these two pieces of information, you now have to deal with figuring out the new offsets for Genesis Plus (easy to do, but just time consuming to do the math).

Some of us here would be glad to help you hack savestates. That includes me, as I love doing it. However, I can't help you out any further than this. I'm just saying it's pretty unlikely.

n45800

One thing to remember, many Mac emulators gzip their save data. Be sure to extract / edit / recompress the data, or else you will be dealing with pseudorandom compressed gibberish.

seanstar

If you can get your hands on identical-state saves for the two emulators (saves made at the same point in the game with the same saved content, e.g. perhaps the very first point in the game you can save) and account for the un-gzipping as needed, you may be able to eyeball the two saves side by side in a hex editor and spot where a recognizable chunk of bytecode starts in each. The structure of the file will likely be an emulator-specific header (which may even be nominally human-readable) followed by some possible padding bytes followed by banks of game memory, likely in easily-Genesis-addressable-sized chunks. I'm not certain architecturally what addresses on Genesis are writeable, or whether different games used different or unusual banking or addressing hacks, so it may be more convoluted, but that would be a starting point. You may even want to look at multiple uncompressed savestates from multiple games to see whether you can work out how big the headers are, since they're probably a fixed size for all files. Once you know what the offset is between where data is in the two savestate formats, ~hopefully~ the layout of the save data itself is consistent and identical to the layout in Genesis memory, meaning you can just offset the addresses given in the instructions and edit those bytes in the Mac save.