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I was watching a channel about living in China. And the host present a Jacky Chan Nintendo Fake.

Sales box containing fake

System looks like a Famicom. But when show the cartridge Video, looks they need batteries.

Cartridge

Then it mentions a need for a battery to save games.

So I was wondering what happen if the battery ran out. Do you lose your saved games?

  • I'm curious in what way does it "look like" a Famicom? Do you mean the games remind you of Famicom games? The console itself looks like a full keyboard with a cartridge slot. – RichF Jan 31 '18 at 15:23
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    I love the full IBM keyboard! I had a quick read up on it and found out from e.g. kotaku.com.au/2013/11/… that there was a ban on selling games consoles in China, hence the repackaging as an educational study tool. – Tommy Jan 31 '18 at 15:23
  • @RichF Sorry for the misunderstanding. During the video the host show the manual (4:50) and there is a picture of a Famicom instead of the Keyboard. And because in China fake system are very common I use the similar to Famicom sentence very lightly. Also the cartridges are very similar. – Juan Carlos Oropeza Jan 31 '18 at 15:25
  • It looks 'like Famicom' with the fact that it uses Famicom cartridges. – lvd Feb 1 '18 at 15:15
  • Also it was quite common even for licensed famicom/nes games to have battery-backed RAM, just first example from gооglе: youtu.be/_NXBrAJIbfg?t=58 – lvd Feb 1 '18 at 15:17
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So I was wondering what happen if battery run out. Do you lose your save games?

In an unplugged/stored cardridge yes. After all, they are RAM based.

Now, if it's still pluged and powered, then usualy not. Ofc. it depends how it's wired. With standard circuitry that's also the way to change batteries before they go dead.

  • So you have to change batteries while the cartridge is plug on the system? Do you know when battery power is low and need replacement? – Juan Carlos Oropeza Jan 31 '18 at 15:06
  • No. Keep in mind, this isn't exactly for long time storage. – Raffzahn Jan 31 '18 at 15:12
  • Obviously the trick is to use two pairs of rechargeables (voltage permitting), swap them every week or so and then charge the pair you took out. That being said, can we be absolutely sure there isn't a Z88-esque system at play here, with an internal capacitor that's intended to supply charge for 'long enough' for an unpowered battery swap without data loss (still assuming you magically know when to replace)? – Tommy Jan 31 '18 at 15:15
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    @Tommy usually not, as these Chinese clones are about reducing cost. and ratehr large caps wheren't cheap back then. Only taking it apart might tell. – Raffzahn Jan 31 '18 at 15:21
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Many cart-based games used battery-backed SRAM for storing saved game state. The RAM was usually powered by a lithium coin cell that could keep the RAM contents powered for a number of years. Once the battery died, the cartridge lost the ability to store game save data. While the cart was plugged in, the console would power the SRAM so the game would function normally, and even appear to allow a save, but as soon as you removed power, all saves would be lost. The game itself is still stored as permanent ROM, so a dead battery will usually not make the game unplayable, it'll just mean the game can't save stage that will survive between power-ups.

Some carts used soldered versions of lithium cells (they made/make lithium cells with solder lugs permanently welded to the battery) while others, more rarely, used a socket, allowing the battery to be replaced easily after opening the cart. I have personally replaced the soldered cell on a few carts for myself and friends with a socket for a CR2032, the same cell used on most PC motherboards.

At the time these techniques were popular, flash memory was still new enough to be disproportionately expensive compared to SRAM + the battery. Flash also has the disadvantage of being slower than SRAM, so if the game used the SRAM for game logic, flash would have been impractical. Finally, if you think the write endurance on modern flash is bad, the endurance on early flash was even worse, so depending on how often the device wanted to write to NV storage, flash could easily have been worn out whereas SRAM has virtually unlimited write cycles.

Using batteries for nonvolatile memory was done in lots of devices in the 80s and 90s. I had a PDA that used a lithium coin cell for its main RAM, and after that cell died the PDA would "hard reset" each time you powered it off and back on. (I replaced that cell with a socket as well) Other devices that ran on user-replaceable batteries would often include a capacitor that could maintain the RAM contents for a few minutes to allow you to change the batteries without losing data. Others still included the lithium cell along with the user replaceable batteries; the lithium cell basically kicked in whenever the main batteries were low or missing.

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