[NTLK] flash longevity question

[Dan]

Wow Victor!  Thank you!  I knew that the chips were NOR but I have heard the phrases used interchangeably with NAND.  A large mistake as they are very different.  I suspected as much but couldn't find the details when I looked.  Apparently I was using the wrong search terms.

I did have a hunch the older, less dense chips would be a world of difference with regard to longevity.  What IS fascinating to me is the large push for the flash drives when there is a obvious longevity problem, and no one talks about this.  Sure for the moment it is fine and if you are using it not for long term storage no problem.  But consider how many devices have these chips in them which most people think 'flash is forever' if it is just sitting there which is not the case.

I think of all the devices with these chips embedded such as game consoles and other devices.  Older consoles from the 80's are still playable, but newer ones such as the Wii, Wiiu, etc sound like they won't going into the future.  With the Wii and Wiiu, for example, their OS is in flash.  Very little is in ROM type chips.  The bootloader perhaps, but that is all.  Softmodded units you might be able to reinstall the data should it 'fade away' if you had a backup.  But that is something the moders don't recommend doing unless you have the equipment and skills to remove the NAND chip as it is prone to failure reinstalling the backup to the NAND chip.  And if it does, that is the only way you can get the unit operational again.

Sure everything can fail, but these have a lot less longevity than previous technology and sounds like a step backwards except for capacity.  Almost makes you wonder if that was by intent.  Give them a lot of capacity, but short life, keep 'em coming back for more.

-Dan

On 9/13/2022 11:38 PM, Victor Rehorst wrote:
> Modern flash memory chips use multi-level NAND gates packed hundreds (if not thousands?) of times denser than the single-level cell, NOR-based chips used for any Newton, or compatible linear flash cards. They're different beasts designed to perform different jobs.  So I don't think that the durability (ability to retain data when unpowered) of high-density NAND flash can be compared to NOR flash from many generations ago.
> 
> (6) is a good summary of the differences between NAND and NOR in terms of reliability.  Particularly interesting tidbit from that article is the note that reading from modern NAND devices can eventually disturb adjacent cells and cause data loss; NOR does not have this problem.
> 
> And then I did a research deep-dive ...
> 
> NOR flash uses the same technologies as EEPROMs, except the latter can be erased and reprogrammed at the byte level, whereas NOR flash can only be erased at the device (chip) or block level. The durability of EEPROM and NOR flash should therefore be comparable, as long as the same silicon processes are used.
> 
> This PDF from Intel(1) in September 1994 talks about the differences between Intel Series 1, Series 2, and Series 2+ flash cards.  All of these use chips with "ETOX" or EEPROM Tunnel Oxide technology.
> 
> I found this paper(2) from Proceedings of IEEE in 1993 that examined the reliability of different flash memory technologies, specifically ETOX type as well as NAND type.  The paper cites another (3) which mentions that ETOX-type flash was tested at 250°C for 168 hours and 10,000 erase/program cycles, and the stored voltage was still well within readable parameters.
> 
> This "bake" test sounds like a less formal version of the standardized reliability tests now performed on some flash chips. As far as I can tell, no such standard existed in the 1990s, unfortunately, but with today's standardized tests and some mathematical models, we can extrapolate some expected durability performance.
> 
> For example, some test reports from STMicro state some data retention safe values:
> 
> * more than 200 years at 55°C or less for high density EEPROMs (4)
> * more than 40 years at 55°C or less for EEPROMs embedded within NFC chips (5)
> 
> All this to say that temperature is probably the most important factor when it comes to storage durability of flash.  Also, I'm not worried about the data on any of my Newtons; I'm pretty confident I'll boot one up in another ten years and everything will still be there.
> 
> -Victor
> 
> 1) http://intel-vintage-developer.eu5.org/DESIGN/FLCARD/APPLNOTS/29215801.PDF
> 
> 2) https://www.slac.stanford.edu/exp/npa/misc/00220908.pdf
> 
> 3) https://ieeexplore.ieee.org/document/572591
> 
> 4) https://www.st.com/resource/en/application_note/an4653-cycling-endurance-and-data-retention-of-high-density-eeprom-based-on-cmos-f8h-process-stmicroelectronics.pdf
> 
> 5) https://www.st.com/resource/en/application_note/an5085-cycling-endurance-and-data-retention-of-eeproms-in-products-of-the-st25dvi2c-series-based-on-the-cmos-f8h-process-stmicroelectronics.pdf
> 
> 6) https://www.curtisswrightds.com/sites/default/files/2021-10/Flash-Memory-Lifespan-and-Reliability-white-paper.pdf
> 
> 
> On 2022-09-12 22:15, Dan wrote:
>> Hi all,
>> I always thought that while flash had a limited number of write cycles, the actual data storage was pretty reliable.  But recently I have run across several papers that say long term storage isn't a good idea and will eventually fade away (giving a general time frame of 10 years).    Never heard of that before, and we have often talked here how a "newton never forgets" after being in a drawer for over a decade and everything is still intact as the day we put it there.
>>
>> Is this situation with flash something that has recently been found out?  Or is it the newer flash chips have such extreme density that they deteriorate in 10 years?  Such as MLC or even TLC vs SLC.
>>
>> So far all my cards still have all their data and are functioning fine.
>>
>> -Dan
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