So recently I've been experimenting with ways to eliminate the need for batteries on various hardware that uses them to keep save games. I first had the idea when I opened up an N64 Controller Pak, and to my surprise, rather than flash memory used by the PlayStation, Nintendo opted for a volatile SRAM chip with a battery to keep data intact. Now, it being the future, I wanted to know if there existed a way to replace that chip for something non volatile, and eliminate the battery altogether. As it turns out, the SRAM chips used on those memory cards, are usually something akin to the LH52256 - a 256kb chip, and to my surprise, there exists a completely pin compatible 256kb non volatile FRAM chip, designed as a drop-in replacement - the FM18W08. This actually works like a charm, and that memory card no longer requires a battery. So after this, I wondered about other things that use volatile SRAM and a battery, so I cracked open a couple of my SNES cartridges, Super Mario RPG and Yoshi's Island to be precise, and lo and behold, both of these games also use some variant of the LH52256. Naturally, I swapped these chips out and inserted an FM18W08 in their place, expecting similar results, however, sadly this was not the case. I have read on this guy's blog
that he has had success when doing something similar with other SNES games, albeit with lower capacity chips, but with 256kb FRAM chips, both Yoshi's Island and Super Mario RPG crash on startup and do not run.
Anyway, after all that, does anyone have any ideas about how I might be able to get this working? Thanks!