Modifying the SEGA SATURN to use standard SRAM backup/disable RTC.

Is there even an extra address line for it? Or is my understanding of this incomplete?

 

This is from my possibly imperfect memory, but I think it's connected to the same bus as the boot ROM, and that's 512KB, so at least up to A19 should be available.

I also remember that it was mirrored multiple times (0x180000-0x1FFFFF?), so there shouldn't be a problem with decoding. Oh, and it's an 8-bit device wired to a 16 bit bus, so although it's a 32KB RAM it occupies 64KB of space with only each alternate byte used. I can't think of any electrical reason it shouldn't work, as long as the routine that initializes the memory is written to check for other RAM sizes.

 

How about replacing the SRAM with FRAM?

Would this be a sufficient replacement:
http://www.ebay.com/itm/FM1808-70-S...P-28-256Kb-Bytewide-FRAM-Memory-/261333829598

 

Hate to be "that guy" but due to the Saturn's power supply being physically turned on / off rather than controlled by software, the fact that the system is plugged in probably does nothing to the life of the battery backup. The circuit is physically broken.

 

I did this crap in 2011, I just finished servicing the Saturn board for bad capacitors, it still has the very same battery I put on it in 2011 and it still has the data in it.

Of course FRAM is simpler and easier.