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Sonic 3 FeRAM Adapter

Breakout/adapter board for replacing the FeRAM chip in a Sonic 3 cartridge with a modern chip.

Clayton G. Hobbs
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I have a Sonic 3 cartridge for the Sega Genesis that doesn't save any games. Unlike many other old cartridge-based games that use a battery to retain the contents of volatile memory, Sonic 3 used a non-volatile ferroelectric RAM (FeRAM) chip for storing its saves. Sometimes these wear out and need to be replaced. Similar modern chips exist, but in surface-mount packages and with more capacity than the original. This project is an adapter board to put one of these modern FeRAM chips into a Sonic 3 cartridge.

The Sonic 3 cartridge contains an FM1208S FeRAM chip for storing its saves. This chip is no longer produced, but a similar, higher-capacity chip, the FM16W08, is. By pulling the extra address lines to constant levels, we can pretend the new chip is only 512 B like the original. Since the new chip is a small(-ish) SMD, the old one was a huge 600 mil 24-pin DIP, and their pinouts are similar, making an adapter board is simple.

  • 1 × FM16W08
  • 1 × PCB Not just any PCB, specifically the one from the linked Git repository
  • 1 × Sonic the Hedgehog 3 cartridge Specifically, one with a bad FeRAM chip
  • 1 × Reasonable length of bare 22 AWG wire You can make this from insulated 22 AWG wire, some wire strippers, and a lot of patience

  • Complete!

    Clayton G. Hobbs • 02/27/2017 at 19:29 • 0 comments

    I completed this project shortly after writing the last log, but didn't bother writing anything about it at the time. The idea I got there of putting the boards flat against each other worked fine, and I didn't need any Kapton tape between them either. So now I've gone from having a Sonic 3 cartridge that won't save, to having a Sonic 3 cartridge with 16 cumbersomely-switchable memory banks. Plus, the new chip is rated for 10,000 times as many read/write cycles as the old one, so it shouldn't need replacement until long after I'm gone. Thanks Cypress for continuing to make compatible chips!

  • Note to self: check dimensions before ordering parts

    Clayton G. Hobbs • 09/17/2016 at 01:34 • 0 comments

    I was originally planning to use two machine-pin headers to connect the adapter board to the cartridge board. Then I found this neat part at DigiKey and I decided it would be nice to use one of those instead. I got one, and after removing the old FeRAM chip, I found that the new socket is too tall to fit in the cartridge. I also found that with the thickness of the new FeRAM chip stacked on top of a 1.6 mm PCB seated on that socket, the cartridge will have no hope whatsoever of being assembled. Heck, I'd probably have to cut a hole in the front for the new FeRAM chip to stick out through. It should be needless to say that this would be unacceptable, so I won't bother saying it.

    What to do then? I looked at the original board, checked some thicknesses, and got an idea. Just put a piece of Kapton tape where the new board will go (merely for paranoia, probably not needed) and connect the two PCBs together with short pieces of bare 22 AWG wire. The whole assembly will be around the original thickness, or maybe even a little less. Everything will probably work out fine.

View all 2 project logs

  • 1

    Identify that your cartridge needs FeRAM replacement. If the save game feature simply doesn't work, that's a good indication. 😉

  • 2

    Order all the parts needed. The FM16W08 chip costs around $10 at quantity 1 from most electronics wholesalers at the time of writing. You could order the circuit board from your favorite fab house, or I could send you one at cost since I currently have two extras.

  • 3

    Open the cartridge. They use some stupid security screws, and I've seen various ways of opening them ranging from melting pens to buying special screwdrivers. I find that just using a 4 mm hex driver and applying a lot of force, I can reliably open Genesis cartridges, so I recommend you try that if you already have a 4 mm hex driver.

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Adam Vadala-Roth wrote 02/27/2017 at 18:22 • point

I still got this game on cartridge, I think mine still saves though, keeping an eye on this project in case mine fails. 

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