http://nintendoage.com/forum/ -Sqooner http://nintendoage.com/forum/messageview.cfm?catid=22&threadid=148649 2015-06-20T02:49:06 -05.00 a0r10n 6
The solution I would recommend, if preserving the data is important enough, is doing a CRC on the save data, and storing multiple copies in RAM. If the CRC fails, there's a good chance you can load one of the backups.

Like Guntz mentioned, MMC6 is one mapper that has battery-backed RAM dedicated to saving (much smaller though, and built-in to the mapper). From what I understand, games like Star Tropics would enable the backup RAM only when saving data, so it's RAM is almost always disabled. I would imagine a game like Genghis Khan (which has 2 8kB RAMs) does something similar. It's always possible to throw hardware at the problem, just costs a bit more to make the cart. For a "modern" NES game, I would recommend using FlashROM to save. It's much harder to corrupt, because every write requires an unlock sequence. There's still the problem of a user powering down while a write is happening, but little else to worry about.

If you're in the early stages of development, it's probably better to worry about a more robust save system later on, it's something that should be easy to change, if you have a little bit of a system to it. I'd say basically to only write your actual save data all at once, and when manipulating it, do it on a temporary copy in another part of RAM. You'll be able to get it working, data corruption in SRAM is just a fact of life (at work I repair/refurb a Z80-based system with a similar setup, and see it all the time), every NES game dealt with it in some way, except I guess the few that threw more hardware at the problem. ]]> http://nintendoage.com/forum/messageview.cfm?catid=22&threadid=148649 2015-06-19T23:28:57 -05.00 a0r10n 6 http://nintendoage.com/forum/messageview.cfm?catid=22&threadid=148649 2015-06-19T20:47:56 -05.00 a0r10n 6 http://nintendoage.com/forum/messageview.cfm?catid=22&threadid=148649 2015-06-19T03:18:03 -05.00 a0r10n 6 http://nintendoage.com/forum/messageview.cfm?catid=22&threadid=148649 2015-06-19T03:02:41 -05.00 a0r10n 6
As far as I'm aware, you can't save parts of WRAM, the whole 8K block ($6000-$7FFF) is saved if a battery circuit is present on the cart. ]]> http://nintendoage.com/forum/messageview.cfm?catid=22&threadid=148649 2015-06-19T00:14:36 -05.00 a0r10n 6