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Is there a standard number of bytes a Game Boy game would have to store (battery backed up) save data?

If not a standard, is there an common size, or a few examples of save data sizes?

If Game Boy is not known, I'd be happy with the same information for NES.

Thanks!

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Here's a map of the cartridges. It notes that

MBC2 has 512 * 4 bit of internal memory used as back-up memory. It is accessed using A8..A0 and D3..D0.

and that

The back-up memory is preserved by a 3V lithium battery together with a NV-RAM controller.

This reference of Game Boy information may be of use to you.

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I do not know what you mean by battery backed up, since (as far as I know) cartridges use capacitors to save the bits. The game progress is stored inside the cartridges.

ROM: On-CPU-Die 256-byte bootstrap;[26] 32 KiB, 256 KiB, 512 KiB, 1 MiB, 2 MiB, 4 MiB and 8 MiB cartridges

https://en.wikipedia.org/wiki/Game_Boy (source wikipedia)

If you mean internal storage these specifications may help you http://gameboy.mongenel.com/dmg/asmmemmap.html

Also see the reply of HardToFocus on how to save to cartridges: https://retrocomputing.stackexchange.com/questions/6405/game-boy-save-problem

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  • \$\begingroup\$ What I mean is that on some games, the user is able to save their status on the game cart (rather than starting from scratch or using passwords). This is done by storing the game state in memory. That memory is kept active with a small watch battery (or else it would reset every time you turned off the console). My question specifically, is how much space (in bytes) did the developers how to work with. eg. "Games had to compress the game state into 4 bytes of space." \$\endgroup\$ – Goose Aug 25 '19 at 21:57
  • \$\begingroup\$ 256 KiB, 512 KiB, 1 MiB, 2 MiB, 4 MiB and 8 MiB cartridges were used by the original gameboy (source wikipedia). I don't see a problem in using this space to store data, rather then read only data from it. But maybe intern mechanics forbid this. But I guess you can use the space that is left free when your game is build to the cartridge \$\endgroup\$ – yesyoor Aug 25 '19 at 23:37
  • \$\begingroup\$ Nah, its not the same thing. \$\endgroup\$ – Goose Aug 27 '19 at 3:19
  • \$\begingroup\$ oh okay. so it is not possible to change values in this cartridge memory while the game is running? You can only read from it? \$\endgroup\$ – yesyoor Aug 27 '19 at 10:52
  • \$\begingroup\$ That's what ROM stands for: Read Only Memory — no writing allowed. Games with a save feature had a separate bank of writable / volatile memory that had to be kept powered with a built-in battery or capacitor to avoid loss of data. \$\endgroup\$ – DMGregory Sep 23 '19 at 13:09

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