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N64 Controller Pak F-RAM Mod, Done Properly

August 18, 20222 threads~1 min readSuccessful repair
Battery-backed save loss
Save battery / FRAM mod

F-RAM upgrade across a couple of N64 Controller Paks, no more batteries quietly erasing your saves. Revisited years later and redone properly, following nosIndulgences' research: the quick version can corrupt data in the long run, so this one adds a pull-up on the write-enable line.

Parts & Tools (2)

Cypress/Infineon FM28V020-SG (F-RAM)

FM28V020-SG, a 256Kbit (32K x 8) parallel F-RAM in a 28-pin SOIC, rated 2.0V to 3.6V, with 70ns access. It drops into the U2 "S-RAM" position in place of the original battery-backed SRAM, so the saves are held with no cell at all. Originally a Ramtron design: Cypress bought Ramtron and Infineon bought Cypress, so the same part turns up under all three logos depending on when it was made.

Mind the voltage rating when picking a chip for this. The N64 feeds its controller port 3.3V (3.36V measured on a real console) and the Controller Pak runs off that through the controller, so it needs a 3V-rated part. The FM1808 that often gets used for this mod is the 5V member of the same family, rated 4.5V to 5.5V, so at 3.3V it sits below its specified minimum. The pin-compatible 3V equivalents of the FM1808 are the FM18W08 and FM18L08.

Bourns CRT0603-BY-1002EAS (10K 0.1% thin film resistor)

CRT0603-BY-1002EAS, a Bourns thin film chip resistor, 10K at 0.1% in an 0603 package, sourced from Mouser. Fitted as a pull-up on the write-enable line. This is the part that keeps the saves from corrupting over the long haul, and it is the step the quick version of this conversion leaves out. The method follows nosIndulgences' research, linked in the thread above.

A note on the size: 0603 does work, and the second pak here was opened up to show it, but it takes a steady hand and it will not comfortably span the pad area left behind by the removed power management IC, so it tends to end up mounted elsewhere with wires run out to it. An 0805 overlays the relevant pins directly and bridges only what it should, which will be easier for most people.

hitmanmcc
hitmanmcc

August 18, 2022· Thread 1

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Tea break upgrade. #N64 controller paks fitted with F-RAM. No more batteries for these boys. #Nintendo #RETROGAMING #consolemodding

hitmanmcc
hitmanmcc

September 29, 2026· Thread 2· 3 tweets

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Finally circled back to fix something here. As per @nosIndulgences' research (https://x.com/nosIndulgences/status/1831342825926951227), this is the proper way to do this mod, in order to avoid data corruption in the long haul. Sadly, I couldn't make this as neat as I wanted to, my 10K resistors are too small.

2 / 3

And here's the second pak. @misirajeduart.bsky.social was complaining so I opened up that one too in order to show that 0603 can work with a steady hand.

3 / 3

Also re-did the first one.

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