Battery Backup

[cornsyrup32]

Hi, I have been doing nes reproductions for a while and I came across this site - nesreproductions.com. I looked at some of his games and they were cool, but what caught my eye is that he said he charged a $3 fee to add a battery to a game that did not have one. That would be useful so I don't have to find a tkrom cart every time I want to do a battery backed game.


Thanks so much,
Brandon

[Pasky]

Ya, thanks for blatantly advertising stupid repros.

[OneCrudeDude]

Actually what he means is that he charges you $3 to replace a dead battery in a cartridge, he doesn't add anything new. Still don't know why this warranted a thread, and I don't know why I replied.

[cornsyrup32]

Look at his battery backed game

[OneCrudeDude]

Ah. I'm still more concerned with how you can add a whole function to a board that was never made for such a thing in the first place.

[tepples]

SNROM has a space for a battery backup circuit that's not populated on all boards. If it's not populated, it's as if that part of the board weren't there. But because the MMC3 needs a bit more space on the board, Nintendo made separate boards with and without the battery pads. TKROM is PRG ROM + PRG RAM + CHR ROM + MMC3 + battery pads, and TSROM is the same thing without battery pads. These "$3 extra" games appear to be TSROM, and adding the additional components (a battery and some passives) makes the board functionally equivalent to TKROM.

[cornsyrup32]

SNROM has a space for a battery backup circuit that's not populated on all boards. If it's not populated, it's as if that part of the board weren't there. But because the MMC3 needs a bit more space on the board, Nintendo made separate boards with and without the battery pads. TKROM is PRG ROM + PRG RAM + CHR ROM + MMC3 + battery pads, and TSROM is the same thing without battery pads. These "$3 extra" games appear to be TSROM, and adding the additional components (a battery and some passives) makes the board functionally equivalent to TKROM.

Ah, do you know the passives you would need, kinda a newbie.

Thanks so much,
Brandon

[nintendo2600]

I think the OP means adding the battery circuit so the SRAM keeps the save data buy using a pair of diodes, a resistor and a cap. If he was able to google how to build his repro's he should also be able to google the battery circuit. Hell I think it's even on this forum somewhere.

[mikejmoffitt]

Wait, do those games suddenly support saves if supplied with the proper components?

[Ice Man]

They always did. You only have to add the battery connected to diodes, resistors and capacitors. Not hard at all.

[nintendo2600]

They always did. You only have to add the battery connected to diodes, resistors and capacitors. Not hard at all.

Yep exactly like that

[Ice Man]

While we're at it.
I've wanted to convert SLROM to SNROM or even SKROM.
While replacing the CHR ROM with CHR RAM isn't trivial I was wondering how exactly would I need to change the MMC1 chip, since the output of the legs is different in different boards. o_O

[lidnariq]

http://wiki.nesdev.com/w/index.php/MMC1_pinout

[Ice Man]

So basically I just lift those pins and reconnect them (or leave them NC) to the CHR/PRG/WRAM, correct?

[Bavi_H]

Wait, do those games suddenly support saves if supplied with the proper components?

Just to be clear, in its original context, the picture cornsyrup32 attached above doesn't imply the games (software) in red can make use of battery saves. It only means if a battery is added to the hardware, then the ROM can be replaced with a game that does use battery saves.

The list shows what compatible donor cartridge you need to provide if you want that site to burn, for example, Earthbound. On that site, you can scroll down to Earthbound and click the circuit board to see the list in context:

This reproduction requires one of the following donor carts; no other game will work. You must send us one of these games to be converted to the reproduction of your choice. If you're unable to find any of these games, e-mail us, we sometimes have extra donor carts which we sell at cost.

Games in RED can also be used, but an extra charge of $3 will apply to upgrade the game to use a battery.

In other words, that site is upgrading the final burned game (upgrading the donor hardware), not upgrading the original donor game.