Hacking Are DS Game .sav files region interchangeable?

[Garo]

If I started a file with the japanese Fire Emblem DS game and then switched ROMs to the US version (whenever it comes out), will it go smoothly?

What if I used the english patched version for the first ROM?

Is there a general rule or is it game by game?


Also, is it possible to alter the ROM by switching out game songs with other songs? Such as removing the title song of a game and instead putting in the Super Mario Bros. theme (for example)? (I would like to know for DS roms and SNES roms...)

Also, where can I find what the DSi store has available in japan? I would like to know because I want to intercept a release I think could happen.

Also, is game coding difficult? I don't know anything about it, but I'd like to do a lot of things if it was reasonably simple... But why would I think it is?
(Examples include translating ROMs, modifying snemulds, and other stuff)

 

[Destructobot]

If I started a file with the japanese Fire Emblem DS game and then switched ROMs to the US version (whenever it comes out), will it go smoothly?

What if I used the english patched version for the first ROM?

Is there a general rule or is it game by game?

It depends on the game. Some games use compatible save data for the different regional releases, but most don't. The only way to find out if the saves are compatible between releases it to try it.

Language patches generally do not affect the save data at all, so that would not have anything to do with the save being compatible with different regional releases.

 

[Garo]

All right, thanks for confirming my intuition.

Now about the coding...

 

[AXYPB]

In my experiences, unless a game was changed significantly between regions, usually a save will work for all regions. You should be cautious with specific barriers, such as inputted names and other things, especially if the English release doesn't allow for Japanese user names, etc. Having said that, however, it's always worth a try, and if you backup your original files, you have nothing to lose.

As for coding, resources like http://www.romhacking.net and ROM hacking forums on sites like this are useful.