??'s on Longevity of Flash Memory

[nightrnr]

I perused a few other topics about this, but decided I had some more specific questions on the matter.

1. How many times can you save on a game that uses flash memory
*The manual for Doom on Atari Jaguar estimates 100,000 saves.
*I've heard that flash memory can be as low as 10,000 changes.
*My copy of SvC: Card Fighters Clash has at least several thousand changes on it, how much more do you think it's got left?
* Anyone know how many changes PS1 and PS2 memory cards can handle?

2. If file containing several other files (let's say 100) is over-written several times (let's say 10 times), does that mean that it's the sum total of all those files (10x100=1000 save changes)?

3. Does a higher capacity memory card mean more possible save changes? Let's say you have a 1GB card and an 8GB card and that they both supposedly spread out the saves to increase the life expectancy. Does the 8GB card have 8 times the saves (changes), or is it the same as the 1GB card?

4. If the flash memory is maxed out, will the last save file(s) still be intact (even if it cannot be changed), or does it no longer retain ANY saves (like if it used a battery instead and it died).

If anyone can shed some light on the subject for me or at least point me to a place that can, I'd be grateful.

[MrPopo]

Essentially every discrete block on flash memory can be written X times. A halfway decent flash interface will spread your writes over the entirety of the memory in order to help spread out the wear. The reason it can do that is that when you delete a file from flash memory it doesn't actually remove the data; instead it updates the index of where everything is to say that that section of memory is fair game. So deleting a file is a smaller update, and then future writes can use that memory. Capacity in-and-of itself is not an indication of writes. It's more a function of the quality of the memory. Modern cards are better than older cards.

[Hobie-wan]

I think the lowest number I've ever seen for early flash memory is maybe 10K, but newer stuff should be more robust. It still has its limits though. The thing about flash memory is that all (or at least most) of it doesn't just write at the beginning every time. So if you write to a blank device it will put the file in one spot. If you erase it and save again, it will actually put it in a different spot. It does this so that it doesn't wear out the same spot and instead shuffles around the usage to try and wear it evenly.

Once it does reach its limit it will just start to break down. You might have a file that goes corrupt and can no longer be read. If you keep using it, maybe next week you save something else that can't be read later. If the bad spot is part of the file table, you might lose everything at once since it would no longer know what file was where. Short of cracking open the chip and looking at it under a microscope I don't think there's a way to tell how much life there is left until things start acting flaky. Of course opening up the chip would probably destroy it as well.

[nightrnr]

Thanks you 2! That answers some of my questions.
I'm one step closer to uncovering the unfathomable secrets of flash memory.

Okay, let me pose another situation, just to clear it up for me:

Tom and Jerry both have their own memory card.
Tom saves over a single 10MB file once a day.
Jerry saves over ten 1MB files every day.
Tom and Jerry are immortal and plan on repeating this routine until one of their cards dies, after which they will fight over the surviving one.

So which memory card bites it 1st?
If I understand it correctly, Jerry's card endures the most writes and will therefore start failing sooner.
But technically, they are still covering the same amount of blocks right?
But maybe the several smaller saves are spread out to different and possibly a greater number of blocks.
So I'm not sure.

[Hobie-wan]

Well, they'd be writing more or less the same amount of actual file data, but Jerry is updating the file table 10 times more often. So ignoring any other irregularities in manufacturing that might make one slightly weaker somewhere, Jerry's would be expected to crap out first.