theoretically changing roms on a cartridge

[OneOwen]

could you theoretically change any data on an official nds/3ds cartridge to homebrew or would you need an r4 card to load homebrew that way, i was thinking if you could hijack the state of saving a game file and edit other contents, or it could be only editing data on existing files? if so would you be able to edit the game files to make a rom hack on an official cartridge?

 

[godreborn]

Not possible. Roms stand for read only memory.

 

[KleinesSinchen]

Read through this thread:

https://gbatemp.net/threads/3ds-cartridge-dump-and-replace.484214/

 

[OneOwen]

Not possible. Roms stand for read only memory.

how do save files get saved because i was thinking at least editing and replacing save files manually or through other means, couldnt you run homebrew by overloading the system memory to run external applications

i was hoping to hijack the process where save files get saved so i could edit other data on the cartridge

 

[Hayato213]

how do save files get saved because i was thinking at least editing and replacing save files manually or through other means, couldnt you run homebrew by overloading the system memory to run external applications

i was hoping to hijack the process where save files get saved so i could edit other data on the cartridge

You can't because the game data is ROM, read only memory. For save data on cartridge you can decrypt it with homebrew like jksv / checkpoint or like cybergadget save editor for Japanese cartridges.

 

[r1vver]

Game data is on MROM (Mask ROM) chip. It's big one on image. It is programmed only once when the chip is produced in the factory (photolithography process). Reprogramming is impossible. Physically impossible (because of the method of production).
Saves are on EEPROM chip. Small one on image.

 

[mrgone]

this is only possible with "modern" gameboy/color/advance games from chinese sellers as these are usually re-produced with re-writable flash memory instead of once-writable maskroms.

 

[KleinesSinchen]

Game data is on MROM (Mask ROM) chip. It's big one on image. It is programmed only once when the chip is produced in the factory (photolithography process). Reprogramming is impossible. Physically impossible (because of the method of production).
Saves are on EEPROM chip. Small one on image.

For DS games true. For 3DS games... I'm missing deep knowledge here... they are technically rewritable on physical level - to my knowledge.
See card1/card2
https://wiki.gbatemp.net/wiki/3DS_Glossary#C

I guess the chip itself will be locked against software attempts to write (outside specified savegame region). Would be a bummer if a software error would end in the game erasing itself.

i was hoping to hijack the process where save files get saved so i could edit other data on the cartridge

We don't need to hijack anything. We have full system control over the 3DS. Besides, editing game data (ROM hack) would end in not working games (on unmodified 3DS consoles).

 

[The Catboy]

I have to ask, why would you want to inject a ROM into a different cart when you could just install a CFW and use CIAs?
https://3ds.hacks.guide/

 

[mrgone]

I have to ask, why would you want to inject a ROM into a different cart when you could just install a CFW and use CIAs?
https://3ds.hacks.guide/

the easy answer always is: because the other person likes it that way
but there could be many reasons:
1. one might not like to mod his 3ds or a custom cart could be a present
2. there are many pokemon enthusiasts out there who make custom carts of rom hacks including custom label
and this is applicable to other games besides pokemon, but i guess they are the biggest crowd

 

[OneOwen]

I have to ask, why would you want to inject a ROM into a different cart when you could just install a CFW and use CIAs?
https://3ds.hacks.guide/

to load homebrew on unmodified consoles or other useful tools without sd card, and i could use a r4 card to do this but thats boring and i want a challenge, but it seems it may be impossible if it is ill just use an r4 cart to do so

 

[KleinesSinchen]

to load homebrew on unmodified consoles or other useful tools without sd card, and i could use a r4 card to do this but thats boring and i want a challenge, but it seems it may be impossible if it is ill just use an r4 cart to do so

Just remember that an R4 is limited to DS mode. There is no (simple) homebrew loading on unmodified consoles.
What comes near your idea – rewriteable storage running software in 3DS mode – is Sky3DS+. But that is limited to unmodified cartridge ROMs from the same region as the console (if no CFW is installed).
You can't just slap any random software on it and expect the 3DS security/DRM garbage to accept this.

 

[The Catboy]

the easy answer always is: because the other person likes it that way
but there could be many reasons:
1. one might not like to mod his 3ds or a custom cart could be a present
2. there are many pokemon enthusiasts out there who make custom carts of rom hacks including custom label
and this is applicable to other games besides pokemon, but i guess they are the biggest crowd

to load homebrew on unmodified consoles or other useful tools without sd card, and i could use a r4 card to do this but thats boring and i want a challenge, but it seems it may be impossible if it is ill just use an r4 cart to do so

Fair enough, compelling reasons and respectable

 

[OneOwen]

Just remember that an R4 is limited to DS mode. There is no (simple) homebrew loading on unmodified consoles.
What comes near your idea – rewriteable storage running software in 3DS mode – is Sky3DS+. But that is limited to unmodified cartridge ROMs from the same region as the console (if no CFW is installed).
You can't just slap any random software on it and expect the 3DS security/DRM garbage to accept this.

im aware of that limitation and plan to start first by getting/making a tool to dump slot 2 cartridges