I’ve replaced battery backed SRAM in several game consoles and other devices with FRAM (Neo Geo CD, Sega Saturn, an HP oscilloscope) and for some it’s drop-in, and in a few you have to bodge some lines.

Won’t that negatively impact the life expectancy of the device? FRAM is rated for trillions of reads and, if the SRAM is frequently read, a trillion reads isn’t that much.

>100 trillion reads per location over 30 years still means you gotta read locations at over 100 kHz 24/7. Not good enough for main memory, sufficient even for frequently accessed configuration values.

Definitely not for running code directly from it (unless it's shadowed to RAM), but for storing config data or checkpoints, it makes sense.

I guess it depends on whether the game cartridges only use it for storing savegames, or as actual additional RAM.

Yes. It'd be a problem for running code directly from it - it'd be better to cache it to DRAM so that all reads would come from DRAM and only writes would make it to FE-RAM.

IIRC, it was a common trick with 286 and 386 PCs, because BIOS ROMs were 8-bit wide and shadowing the BIOS in RAM made it much faster.

The FM1808B and FM1608B might work for you. These are 32Kx8 and 8K×8 FRAM chips with standard SRAM pinouts, in DIP packages. If you don't need a DIP, you have a lot more choices.

The SOIC look like they could work as-is in a gameboy, which (thanks to Pokemon) is the most common request for replacing batteries. The DIPs could be made to work in most NES games too, I suspect.