Flashed NES cartridge advice

Hey there guys.


I was looking at making myself a reprogrammable NES cartridge for running demos and some games on them, and wanted some help with it.


From what I understand I'd need a donor cart with the same mapper as the game I want to program onto it (For my example, donor is Kirby's Adventure and flash is Earthbound Zero, both MMC3 with save feature).
Then, I'd need to remove the PRG and CHR chips, flash my data onto my own EEPROM chips and then solder on DIP-sockets to fit the chips into. After doing this, it should (as long as I didn't screw up) work.


Is this correct? Have I missed off any major steps? Can anyone recommend me an EEPROM chip to use for the PRG and CHR, with pinouts if possible?


Thanks!

 

Almost. There are a few wiring changes that have to be done to support standard EPROMs. Also, make sure you know the difference between EPROMs and EEPROMs.

I have an MMC3 guide on my site www.callanbrown.com. A little long-winded if you already know what you're doing though.

 

Just checked it out, thanks a lot! Good to find an informal guide to making one. I've found other scattered information, but no specifics such as recommended chips etc. I'll report back in a few weeks once I've got the parts and done it.

Thanks!

 

Having a development cart like you describe is good but alot of development can be done with the PowerPAK. The main drawbacks to the PowerPAK are you won't catch power-up/initialization bugs in your programs and demos because the PP will initialize hardware for you to some extent. The other drawback is more complex mappers may not function 100% accurately on the PowerPAK, like MMC3. However the advantage of just writing to a CF card is very nice compared to rewriting FlashROMs and putting them back into their sockets. I recommend having both or if only one go with the PowerPAK since it is more multi-use in one device.

 

Thanks, I've been recommended the Powerpak before, so I may have to look into it. I have another question though.
I have split the ROM into the PRG and CHR, and the PRG splits correctly into a 256kb file, but the CHR only splits into a 160kb file, but it should also be 256kb. Is this an issue? I have heard that you need to use multiplication to make it fill up the EPROM, but I can't see any way to get this to fit.

Edit: Disregard this, I used Ucon64 and it seemed to have fixed it.