Zig's Cart Hacking and Creation Thread
Posted: Sun Aug 20, 2023 7:46 pm
Just a thread for me to document some cart hacking and creation that I'm doing for myself.
Luckily, a lot of Super Famicom carts are still very cheap. So I've been collecting more of them the past few years. I've acquired quite a few Japanese exclusives that have been fan translated. So I'll be patching those carts.
Here's Final Fantasy IV. I used the Namingway Edition v.198d patch for it.
FF4 is only 8Mb, so there's a number of ways you can easily patch it. Like a good old 27C801 EPROM, but that would require removing the mask ROM. A board this size, there's actually enough room to store the removed mask ROM inside the cart shell, which is what I have done in the past. But someone came up with a better idea: Leave the mask ROM in place but deactivate it by clipping a single pin, then install an adapter on the backside of the board. I don't know who came up with idea first, or if a few people came up with it on their own, but a number of people are using this method these days. What I like about it is that you can leave the mask ROM in place, instead of worrying about what to do with it.
So all you have to do is clip the /OE (output enabled) pin on the mask ROM and tie high, and that deactivates the mask ROM. Then you're free to install an adapter board such as this one without any conflicts. Luckily, there's a line of TSOP-48 chips that you can still buy new and are 5v tolerant (a lot of memories these days are 3.3v). So I made a few TSOP adapter boards over the last few years for myself, but have slowly got to testing them. So finally I tested the above board out, at least with an 8Mb chip, and it works!
I also decided to change the battery and CB capacitor. On SNES boards that use a 74LS139 decoder for ROM/RAM (pre MAD-1) there is a 22µF electrolytic capacitor. All SNES carts have a 22µF cap, but pre MAD-1 carts with SRAM have an additional 22µF cap located close to the SRAM chip. It's there to help keep the chip powered when you turn off the console (as it's transitioning to battery power). Later SNES carts that use MAD-1 have a CB cap, but it's no longer electrolytic and I'm not sure of the value. So I'm not sure if it's totally necessary or not, but I've have 74LS139 carts give me problems with SRAM in the past. So any of these that I come across in my hacking, I will be replacing it along with the battery just to be sure. The caps are cheap and I have plenty on hand, so there's no good reason not to.
The only annoyance I've found with this adapter board is J1. I used an 0603 pad, but I found it was actually annoying to close with a blob of solder. I'll have to switch it to something that's easier to bridge with a solder blob. I've used 0805 pads in the past and they were easy to bridge, I thought 0603 would be just as easy but I was wrong. I ended up using a trimmed leg from a cap or resistor (I usually save those for stuff like this).
The reason for J1 is to jumper the /OE connection from the socket to the TSOP chip. If you close the jumper, that connects /OE form the TSOP chip to the mask ROM socket. But if you leave it open, then you can use a jumper wire so you can wire the TSOP chip's /OE to something else. The reason for this is mostly because these 29Fxxx chips that you can still buy new are available in sizes only up to 16Mb. But a lot of SNES RPGs are larger than that. So I have other adapter boards that can be used in conjunction with each other, hence the /OE pad. Hopefully you'll see the other adapters at some point down the road, when I get around to using them in other carts I plan to patch.
Here's that adapter board on OSH Park: https://oshpark.com/shared_projects/6EZ6Yl6I
Luckily, a lot of Super Famicom carts are still very cheap. So I've been collecting more of them the past few years. I've acquired quite a few Japanese exclusives that have been fan translated. So I'll be patching those carts.
Here's Final Fantasy IV. I used the Namingway Edition v.198d patch for it.
FF4 is only 8Mb, so there's a number of ways you can easily patch it. Like a good old 27C801 EPROM, but that would require removing the mask ROM. A board this size, there's actually enough room to store the removed mask ROM inside the cart shell, which is what I have done in the past. But someone came up with a better idea: Leave the mask ROM in place but deactivate it by clipping a single pin, then install an adapter on the backside of the board. I don't know who came up with idea first, or if a few people came up with it on their own, but a number of people are using this method these days. What I like about it is that you can leave the mask ROM in place, instead of worrying about what to do with it.
So all you have to do is clip the /OE (output enabled) pin on the mask ROM and tie high, and that deactivates the mask ROM. Then you're free to install an adapter board such as this one without any conflicts. Luckily, there's a line of TSOP-48 chips that you can still buy new and are 5v tolerant (a lot of memories these days are 3.3v). So I made a few TSOP adapter boards over the last few years for myself, but have slowly got to testing them. So finally I tested the above board out, at least with an 8Mb chip, and it works!
I also decided to change the battery and CB capacitor. On SNES boards that use a 74LS139 decoder for ROM/RAM (pre MAD-1) there is a 22µF electrolytic capacitor. All SNES carts have a 22µF cap, but pre MAD-1 carts with SRAM have an additional 22µF cap located close to the SRAM chip. It's there to help keep the chip powered when you turn off the console (as it's transitioning to battery power). Later SNES carts that use MAD-1 have a CB cap, but it's no longer electrolytic and I'm not sure of the value. So I'm not sure if it's totally necessary or not, but I've have 74LS139 carts give me problems with SRAM in the past. So any of these that I come across in my hacking, I will be replacing it along with the battery just to be sure. The caps are cheap and I have plenty on hand, so there's no good reason not to.
The only annoyance I've found with this adapter board is J1. I used an 0603 pad, but I found it was actually annoying to close with a blob of solder. I'll have to switch it to something that's easier to bridge with a solder blob. I've used 0805 pads in the past and they were easy to bridge, I thought 0603 would be just as easy but I was wrong. I ended up using a trimmed leg from a cap or resistor (I usually save those for stuff like this).
The reason for J1 is to jumper the /OE connection from the socket to the TSOP chip. If you close the jumper, that connects /OE form the TSOP chip to the mask ROM socket. But if you leave it open, then you can use a jumper wire so you can wire the TSOP chip's /OE to something else. The reason for this is mostly because these 29Fxxx chips that you can still buy new are available in sizes only up to 16Mb. But a lot of SNES RPGs are larger than that. So I have other adapter boards that can be used in conjunction with each other, hence the /OE pad. Hopefully you'll see the other adapters at some point down the road, when I get around to using them in other carts I plan to patch.
Here's that adapter board on OSH Park: https://oshpark.com/shared_projects/6EZ6Yl6I