Converting Mother 2 Cart to Earthbound

Since I started messing with SNES cart modifications I couldn’t resist this project, I wanted to convert a Japanese Super Famicom Mother 2 cart into an English Earthbound game.  I guess I might be criticised for passing on information on how to make a fake Earthbound cart.  Earthbound isn’t a particularly rare cart, but it does sell for a lot of money.  The people making and passing off fakes for the real thing are doing this by purchasing various American SNES donor carts and converting them to Earthbound with a flash EEPROM and then applying a fake label.  Obviously I hope no-one uses this info to start doing the same thing, converting the original Japanese Mother 2 cart is more involved than making a fake, and of course the cart is left looking like the Japanese cart still.

If you’ve stumbled upon this page because you’re looking for info on fake Earthbound carts, please take time to look at Earthbound Central, in fact, you should be looking at the main site anyway!  They also have a copy of the Earthbound Players Guide in PDF format.


An example of an Earthbound cart at the bottom, a Mother 2 cart at the top
An example of a Fake Earthbound Cart board

Anyway, an original American SNES Earthbound cartridge has just one MASKROM chip, the Japanese Mother 2 cart has 2 MASKROMs.  Because of this, they are wired up slightly differently, meaning a couple of modifications are required if you want to replace just one of the chips on the Mother 2 cart.  You can leave the second MASKROM on there, as we’re wiring up the cart so that’s configured for just the first MASKROM/EEPROM.

Once you’ve got your 29F032B flashed with the American Earthbound ROM (needs to be headerless so that’s 3,145,728 bytes), and you’ve removed the first MASKROM you have a couple alterations to make, these are the differences I found…

  • Leg 2 is currently connected to Ground, instead this needs to go to Cart Edge Connector 46, which is also linked to MAD-1 Decoder Leg 13 (purple wire)
  • Leg 33 is currently connected to MAD-1 Leg 16, needs to be connected to MAD-1 Leg 4 instead (orange wire)
  • Leg 35 is currently connected to Ground, instead, this should to go to Cartridge Edge Connector 48 which is A22, the 29F032B doesn’t use A22 though, so we can ignore this one.

Thank you to ROMLaboratory for posting such excellent info on the pinouts, it allowed me to compare it to the Mother 2 cart and see how a single ROM cart should be wired up to the MAD-1 Decoder and see what else might be different.

You can either cut the traces leading to/from Legs 2 and 33 and simply rewire them, or you can remove/cut some pins from the TSOP adapter board.

For testing, I have fitted a socket to allow me to test the programmed 29F032.  Later on I would keep a bare cart with a socket fitted to test programmed chips before fitting them to the final board.

Cutting Traces

This photo speaks for itself really, you can see the cuts I made, I just put two slices in with my scalpel, and then dig out the bit inbetween the cuts. (This cart has the security CIC chip removed in these photos, I was playing around with different carts at the the time, and temporarily used it on another cart, a SuperCIC modded console doesn’t need a CIC chip in the cartridge though, so was still able to use this cart to test)

Removing Pins from TSOP Adapter Board

Instead of cutting the traces, you can remove Legs 2 and 33 from the TSOP adapter board (either cut the off or desolder them), and solder the contact points from the adapter board to the relevant points on the cartridge board (if your EEPROM is programmed before you solder it to the cart then just remove the pins before you solder the pin headers into the TSOP adapter board).

Once you’ve soldered the TSOP adapter board onto the cart, you just link leg 33 to leg 4 of MAD-1, and then leg 2 to MAD-1 leg 13.

Testing Cart

Because I’ve fitted a socket to test this theory out, the board won’t fit in the cart shell anymore, and it’s too big to fit in the console.  You can either remove the console case, or if you have an Action Replay or Bridge Adapter (to allow US games to play on a SFC) you can plug the bare cartridge board into that and then into your console :-)  The Bridge Adapter I use is converted from an Import Adapter that had a fake CIC chip in, I removed the chip and added wires so that it now just acts as a extension.  Remember – the back of the cartridge board faces the front of the console!

If that works, then pop it back in the cart case (removing the socket and soldering the adapter board directly to the cart bord if necessary), you’ll have to cut off one of the  internal support posts otherwise it will interfer with the TSOP adapter.


ROM File Update

I used uCON64 to check the original ROM file.  I downloaded and configured the GUI for uCON64 to make life simpler.  You can  use it to remove the header, fix the checksum, check to see if it’s byteswapped etc.  Here’s the info from the file I used.