replacing backup RAM with non-volatile memory

[master_d]

Not sure if this is possible and most would argue it's not even worth the effort, but I was wondering if it would be possible to replace the backup RAM with non-volatile memory chip and completely remove the ni-cd battery from the board. I researched different types of nv RAM and it seems to me that FRAM would be the easiest to use as a drop in replacement since flash memory requires higher voltages to write and the write performance of flash is much slower than that of a SRAM chip. The only catch seems to be that FRAM chips will only allow you to read data after the CE pin transitions from high to lo and this may or may not be the case with backup ram on the MVS boards. Anyone know if this is possible? And would removing the battery from the system effectively kill the real time clock?

 

[xsq]

if you remove the battery, your neo in it's present state won't store data like Time, High Scores and Game Settings (soft DIPs). I guess at least the Clock will stop to work even if it is possible to use non-volatile memory, look at PCs or your Mobile - they all need a battery to keep the clock going (I could be wrong about this though).

Why not replace your NiCd-Battery with a Lithium Coin Cell (and remove the 470 ohm resistor to eliminate the charge circuit), as a lot of people have done? That will get rid of the leakage issue and won't loose you any features...

 

[master_d]

hmmm.. yeah I was afraid of losing the clock. Doesn't really make sense fixing the backup ram causes you break something else. I think I will go the lithium coin cell route. How long do these batteries generally last?

 

[master_d]

going back to this idea of using FRAM to replace the SRAM backup memory chip... I was wondering why the backup ram only holds the last 8 hi-score saves. Is it because the bios is hard coded to utilize a stack of 8 HS saves because the chip cannot hold anymore than that? or are the memory locations of the last 8 hi-score saves hard coded in the bios? If this is the case would it be possible to replace the backup memory with a higher capacity chip to save more if not all hi-scores. I assume we'd need a modified bios that is able to take advantage of the new chip as well... but I could be way off here. I guess my main question is what is limiting the size of backup ram?

 

[xsq]

sorry, can't answer your question but a workaround might be to use UniBios to save your highscores on memory cards. If that is an option, you might want to take a look at NeoTurfMastas' projects (like NeoSafeMasta, NeoCardMasta and SaveMastaOne for example).