NES Save Batteries?

[Spindaboy]

I'm just curious, how did these save batteries function?

[jonk]

I'm just curious, how did these save batteries function?

If I'm not misunderstanding you, then they work pretty easily (and they do eventually fail for all the usual reasons that batteries eventually fail.) The issue relates to "volatile" and "non-volatile" memory. Non-volatile memory doesn't forget things when the power is turned off. Volatile memory does forget everything, so that when the power is returned its values are "random" or else all of the same value. Programs are usually placed into non-volatile memory, so that they are not forgotten when the power is turned off. However, most non-volatile memory has a "cost" to it -- it is hard (or impossible) to modify. (Some is easy, though, such as FERAM/FRAM -- but that is fairly modern and not readily available or cheap to buy.)

To save a game, you need memory you can modify easily. But you also want the game to be recoverable after the power is turned off and then back on, too. Which means it must be non-volatile memory. Before FERAM/FRAM existed, probably the cheapest way to do this was to provide a small bit of low-power SRAM (static RAM can be very low power, though not necessarily, as it depends on a lot of factors) that is "battery-backed" so that it doesn't forget what it is holding. (Normally, SRAM without a battery to help it, forgets everything when the power is turned off.) A tiny current is required to sustain the SRAM memory, usually on the order of 10s or 100s of microamps, and this level of current is almost "perfect" for a lithium button battery (which have shelf-lives in excess of 10 years.) The usual series of button batteries used for these purposes is a CR20xx type. They are all about the same diameter, but different thicknesses and therefore different "total energy" (how long they will last for you.) A CR2025 is thinner than a CR2032, for example, and holds a little less energy. I'm not sure what is used in NES cartridges, but I'd bet it is one of these types. They are pretty much a natural for this kind of use with SRAM.

The IBM PC also uses such batteries in order to "hold" the BIOS settings and the date and time, so that when you turn your computer back on it is able to restore the clock time correctly and boot up properly for you. Similar idea, different use.

If the save battery fails, it's not difficult to replace -- if you are able to open up the cartridge. You will pretty easily see the battery. Just replace it with a new one and that will repair the cartridge so that saved games stay saved, again.

[Bregalad]

They just apply a voltage of 3V to the SRAM chip. It needs 5V to funciton, but 3V is enough to retain its data. The chip do not consume any energy since it is not "moving", just in a steady stade. Just like how when you put a weight on a table, you do not need any energy to retain it here, you only had to spend energy to move the thing up to that level.

But without the table, the weight would just fell due to gravity and crash on the ground. The same thing is similar for the battery, without the battery the voltage would drop down to zero and the SRAM chip content would be lost.

[Retrolife]

They;ve made them better in multicarts the battery won't fail cause it's bigger and better

[henke37]

I thought that multicarts were the opposite, as cheap as they could make it.

[SunGodPortal]

I don't know if or why someone would bother with a mutilcart these days when there are plenty of good flash carts out there.

[Disch]

I don't know if or why someone would bother with a mutilcart these days when there are plenty of good flash carts out there.

I don't know why someone would bother with a cart these days when there are plenty of good emulators out there 

I gave up trying to understand people's weird tastes in stuff.  People do things because they think it's neat.

[SunGodPortal]

I don't know why someone would bother with a cart these days when there are plenty of good emulators out there 

I gave up trying to understand people's weird tastes in stuff.  People do things because they think it's neat.

I do it because I still own a legit Atari 2600, Intellivision, NES, SNES, N64 and PS2. CRT is the way to go with pre-HD systems. It's what they were designed for so they don't require a bunch of extra bullshit to make them display properly and you experience no noticable input lag. Plus, I'm not sure why, but playing games on a PC just isn't as fun to me. For whatever reason I find the experience to be less immersive. I also find it much easier to be comfortable when playing on a TV since I don't have to play with it sitting in my lap.

[jonk]

I don't know why someone would bother with a cart these days when there are plenty of good emulators out there 

I gave up trying to understand people's weird tastes in stuff.  People do things because they think it's neat.

Your point is good. But there are times when using a genuine system with a fancy cartridge is nice, too. It's especially nice in real time programs, if you can find a video arrangement which doesn't degrade playability because of the digital nature. (This can be done with some of the modern video displays, but is a serious problem with many digital TVs. Of course, the older CRT types "just work." Hmm. Speaking of which, it is now almost impossible to fine the fast horizontal flyback section transistors that these older CRT systems required. Unobtainium, now, as these new digital systems don't need them and the high scan rate CRTs aren't made much anymore -- perhaps military?)

My ideal system would be an HDMI stick that I can carry in my pocket and plugs directly into any HDMI video+audio input port of a TV or monitor, needs no external power source hookup (uses RTG technology), emulates everything I care about, and "just works" with any controller you grab up that looks just vaguely close to the original controller. (And there is a "universal" mating plug of similar size to stick on the end of any controller cable end.) We might be a few years from that technology, yet. But I can hope! 

Here's a wifi capable plug about the size I'm thinking here:

[jink640]

My ideal system would be an HDMI stick that I can carry in my pocket and plugs directly into any HDMI video+audio input port of a TV or monitor, needs no external power source hookup (uses RTG technology), emulates everything I care about, and "just works" with any controller you grab up that looks just vaguely close to the original controller. (And there is a "universal" mating plug of similar size to stick on the end of any controller cable end.) We might be a few years from that technology, yet. But I can hope! 

I believe you can make a raspberry pi run off of power from USB, which many TVs have now. Really you can put anything you want on those. The things are nowhere near that small though. 

[shadowmanwkp]

Just did a little research into it, there are HDMI sticks that run off XBMC/kodi, they're about the size of a normal usb stick. Problem is they tend to overheat because they usually don't have a good heatsink. Personally I just use my pc, or grab my phone.

[jonk]

I believe you can make a raspberry pi run off of power from USB, which many TVs have now. Really you can put anything you want on those. The things are nowhere near that small though. 

Yes. I'm currently considering an ODROID-C2, which I have now received, for use as a "smart TV" stick (like the Amazon Fire stick, but without their advertising.) It's quite small, quite cheap, and quite fast. It's 2GHz, 64-bit ARM, with 2Gb DRAM, supports 4k HDMI, and I've added a cheap 64GB SD with 90Mb/s transfer rates as its boot device. That done (soon, with luck) I'll then consider the idea of connecting up an SSD so it can double as a media server for the house. (LibreELEC and OpenELEC.) But one step at a time.

I suppose it could be used for emulation. Recompiling BSNES+, for example. I have found attempts to do DOS emulation here. And this looks interesting and related to SNES emulation (and more.) I've seen discussions about quite a few emulators targeting the ODROID platform, already.

By the way, the C2 runs relatively cool without a fan at full speed. Pretty impressive. I can provide pictures of the unit, box, and extras if anyone is interested. It's small. But not as small as I'd like. (It's not like carrying a usb stick in your pocket, for example.)