Saturn FRAM Mod Revisited

A few years ago, René from db Electronics posted a guide on how to replace the Sega Saturn’s volatile save memory with a chip that retains your savegame files, regardless of the battery.  The original guide was awesome, but I wanted to add a few more thoughts, as I recently did this mod to my Saturn.

First, a quick refresher on the issue:  The Sega Saturn uses a battery to power it’s real-time clock (RTC) and to power the memory chip that contains your savegames.  When this battery dies – and it does often – You lose both the clock settings and all of your savegame files!!!  One way around the issue is to use cartridges that back up the savegame files from your Saturn to the cart.  There are things like the Sega Saturn Backup Cart and Action Replay that can accomplish this, as well as some homebrew solutions.

While that’s a great solution, it relies on you remembering to back up your savegame every time you’re done playing.  The FRAM mod replaces the savegame chip with one that keeps the data without any need for a battery, making the whole thing a non-issue.  Here’s how the mod works:

  • Find the ‘UPD43257B’ savegame chip on your Saturn.  Depending on the board revision, it can be on either the top or bottom of the board.
  • I suggest using a hot air station set to 375 at about 70% airflow to remove the chip.  Voultar demonstrates this exact process in his Saturn video around 6:30 and while his video shows a BIOS replacement, the technique is exactly the same:
  • After the chip is removed, replace it with the FM1808, but lift two pins:  #22 and #28.  Here’s why:

In René’s article, he points out that pin 22 is connected to voltage on the original chip, but needs to be connected to ground for the new chip to function properly.  What isn’t addressed is the power being fed to the new chip;  The power circuit going to the original chip is both 5v from the motherboard, plus connected to the battery circuit.  It’s definitely recommended that you isolate the two circuits as to not cause problems with the new chip.  This can be done two ways:

  1. Leave the battery removed.
    This is totally fine, however what if you (or the next owner) forgets and puts in a battery?  Also, you’ll have to set the clock every time you power on the console.
  2. Power the new chip elsewhere.

In my install, thanks to @leo_oliveira, we were able to lift the voltage pin (#28) from the circuit and power it via 5v from a neighboring chip.  This completely removes the battery from the circuit, making it perfect safe to leave it in.

Now, you can keep your RTC without setting it each time you power on the console!  Also, the battery won’t last any longer than before, as the major power drain is the RTC circuit…but when the battery does die, you’ll just loose the clock settings and not your savegames!

I suggest reading through René’s original post for more info, but hopefully this tip of sourcing voltage to the new chip from a different location will provide a more cautious solution with nothing to worry about in the future.


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