6 ms·

That's also how saves worked on some old consoles like the Game Boy. No flash, you have a SRAM with a battery, when the battery runs out you lose your save.

by simias 8y ago

tjoff 8y ago
That can't be right, I thought. Because it didn't match up with my childhood memories. But, it seems the cartridge itself (and not the gameboy which I incorrectly assumed from your post) has a battery which according to internet[1] lasts about 15 years. https://www.reddit.com/r/Gameboy/comments/4w8xjf/guide_how_to_backup_your_game_save_files/ https://www.reddit.com/r/Gameboy/comments/4w8xjf/guide_how_t...
- MBCook 8y ago
  Right. The SRAM was also on the cartridge. Nothing was saved to the GameBoy itself.
grawprog 8y ago
Ya I knew that. I learned that the hard way after my snes games started erasing the save data when I powered off the system. My nes was fairly dead by that point so i missed those. Then I learned my n64 games would be next.... :( I just couldn't figure why fairly modern CNC machines used the same technology as old video game cartridges.
- kakarot 8y ago
  When did they start erasing your save data? I have a few SNES titles that still save correctly. It depends on if they used SRAM at all, or how the SRAM was used. For example, Pokemon was notorious for killing its SRAM battery early because of running things like a real-time clock. SRAM itself doesn't take a whole lot of juice. Also don't worry too much about your n64 games, most of them used EEPROM instead of SRAM. Some NES and SNES cartridges used EEPROM too, but it was much more expensive at the time. If you have any soldering skills, or even if you don't, picking a up a few batteries and a soldering iron is dirt cheap and you could fix your old games pretty easily.
  - Pulcinella 8y ago
    I’ve heard that Nintendo’s standard was that the battery should last ten years, but I don’t I don’t how true that is. They definitely last much longer. I would imagine that the chemistry in the battery would have a problem (e.g. corrosion) before it runs out of energy.
    - aidenn0 8y ago
      My free with Nintendo power dragon warrior cartridge[1] still saves. In fact of about 20 NES carts with save games, only 1 has needed a battery so far. I expect most to die soon though. 1990; it's the one game I know the year I got it for sure, since it was a promontional giveaway.
- Scoundreller 8y ago
  There are methods to hot-swap the batteries without losing your saves. The annoying thing is that you need a soldering iron on the games. The CNC machine probably doesn’t.
Pulcinella 8y ago
Also, in terms of old video games, this is a visualization of cpu instructions per scan line. https://www.youtube.com/watch?v=Q8ph2OVqZeM https://www.youtube.com/watch?v=Q8ph2OVqZeM Around 8m24s you can see how the cpu pauses while ram is refreshed on the SNES. You can see that it’s basically once a scanlije. I found it helpful to visualize how often RAM has to be refreshed (ballparked).
aidenn0 8y ago
I always thought it would be a fun project to replace the SRAM with MRAM, but MRAM is all 3.3V or less and GB and NES SRAMs were typically 5V.
- jacquesm 8y ago
  Three diodes in series should take care of that, and if you find you need to step up the output voltage it should be possible to either put some fast buffers in between or, alternatively, to replace whatever buffers there are already on the board with ones that are more tolerant to voltage differences on their inputs. It remains to be seen how mcuh the MRAM will like the 5V inputs, that is something the datasheet should be able to clear up.
  - aidenn0 8y ago
    whatever it is would have to be bidirectional, since the same pins are used for input and output. They probably make a level converter designed specifically for sram, but I haven't had time to look for one.
    - jacquesm 8y ago
      A 245 or something like that, of course the speed requirements will be critical. It will be a tricky modification to do properly if you want reliability. In the end it might not be worth it.
      - aidenn0 8y ago
        For gameboy, the pokemon cartridge I checked uses a Hyinx GM76C256CLFW, which is 85ns for address acquisition and 45ns for output-enable to valid data. Tightest timing is it requires only 5ns for ~OE being asserted to the outputs being high-Z. It doesn't multiplex address and data pins, so there are only 8 pins that need bidirectional conversion. The TI SN74LVC8T245 has a max time for OH on the 5V pins of 10ns, which is probably good enough. All the NES games I just tried to check require a security bit I don't have to open, so I couldn't check any of them. [edit] I ordered the right driver bit and amazon suggested CR2032 batteries, which I found amusing.

That's also how saves worked on some old consoles like the Game Boy. No flash, you have a SRAM with a battery, when the battery runs out you lose your save.

by simias 8y ago

That's also how saves worked on some old consoles like the Game Boy. No flash, you have a SRAM with a battery, when the battery runs out you lose your save.

tjoff 8y ago

That can't be right, I thought. Because it didn't match up with my childhood memories. But, it seems the cartridge itself (and not the gameboy which I incorrectly assumed from your post) has a battery which according to internet[1] lasts about 15 years. https://www.reddit.com/r/Gameboy/comments/4w8xjf/guide_how_to_backup_your_game_save_files/ https://www.reddit.com/r/Gameboy/comments/4w8xjf/guide_how_t...

MBCook 8y ago
Right. The SRAM was also on the cartridge. Nothing was saved to the GameBoy itself.

grawprog 8y ago

Ya I knew that. I learned that the hard way after my snes games started erasing the save data when I powered off the system. My nes was fairly dead by that point so i missed those. Then I learned my n64 games would be next.... :( I just couldn't figure why fairly modern CNC machines used the same technology as old video game cartridges.

kakarot 8y ago
When did they start erasing your save data? I have a few SNES titles that still save correctly. It depends on if they used SRAM at all, or how the SRAM was used. For example, Pokemon was notorious for killing its SRAM battery early because of running things like a real-time clock. SRAM itself doesn't take a whole lot of juice. Also don't worry too much about your n64 games, most of them used EEPROM instead of SRAM. Some NES and SNES cartridges used EEPROM too, but it was much more expensive at the time. If you have any soldering skills, or even if you don't, picking a up a few batteries and a soldering iron is dirt cheap and you could fix your old games pretty easily.
- Pulcinella 8y ago
  I’ve heard that Nintendo’s standard was that the battery should last ten years, but I don’t I don’t how true that is. They definitely last much longer. I would imagine that the chemistry in the battery would have a problem (e.g. corrosion) before it runs out of energy.
  - aidenn0 8y ago
    My free with Nintendo power dragon warrior cartridge[1] still saves. In fact of about 20 NES carts with save games, only 1 has needed a battery so far. I expect most to die soon though. 1990; it's the one game I know the year I got it for sure, since it was a promontional giveaway.
Scoundreller 8y ago
There are methods to hot-swap the batteries without losing your saves. The annoying thing is that you need a soldering iron on the games. The CNC machine probably doesn’t.

Pulcinella 8y ago

Also, in terms of old video games, this is a visualization of cpu instructions per scan line. https://www.youtube.com/watch?v=Q8ph2OVqZeM https://www.youtube.com/watch?v=Q8ph2OVqZeM Around 8m24s you can see how the cpu pauses while ram is refreshed on the SNES. You can see that it’s basically once a scanlije. I found it helpful to visualize how often RAM has to be refreshed (ballparked).

aidenn0 8y ago

I always thought it would be a fun project to replace the SRAM with MRAM, but MRAM is all 3.3V or less and GB and NES SRAMs were typically 5V.

jacquesm 8y ago
Three diodes in series should take care of that, and if you find you need to step up the output voltage it should be possible to either put some fast buffers in between or, alternatively, to replace whatever buffers there are already on the board with ones that are more tolerant to voltage differences on their inputs. It remains to be seen how mcuh the MRAM will like the 5V inputs, that is something the datasheet should be able to clear up.
- aidenn0 8y ago
  whatever it is would have to be bidirectional, since the same pins are used for input and output. They probably make a level converter designed specifically for sram, but I haven't had time to look for one.
  - jacquesm 8y ago
    A 245 or something like that, of course the speed requirements will be critical. It will be a tricky modification to do properly if you want reliability. In the end it might not be worth it.
    - aidenn0 8y ago
      For gameboy, the pokemon cartridge I checked uses a Hyinx GM76C256CLFW, which is 85ns for address acquisition and 45ns for output-enable to valid data. Tightest timing is it requires only 5ns for ~OE being asserted to the outputs being high-Z. It doesn't multiplex address and data pins, so there are only 8 pins that need bidirectional conversion. The TI SN74LVC8T245 has a max time for OH on the 5V pins of 10ns, which is probably good enough. All the NES games I just tried to check require a security bit I don't have to open, so I couldn't check any of them. [edit] I ordered the right driver bit and amazon suggested CR2032 batteries, which I found amusing.