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eprom based games. how long do they really last?


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so over the years  of collecting when i first got in to test cart collecting 10 years ago i learned about eproms  and that they are not a forever solution and that eventually the data will die of bit rot.

 

however when does that actually happen?  ive heard mixed answers on this from 10, 20, 25 ,50 even up to 200 years according to  some manuals that came with the eproms.

 

and ive personally seen atari 2600 prototypes that still work perfectly fine  and heard of bios chips out of old computers from the mid 70s that still work.  im personally ready for the day bit rot happens as ive already back up my eprom carts  and have a programmer desoldering gun and uv light to restore the data them.

 

but is there a definitive answer to how long the data actually last?  or is it just how the chips are manufactured/how well there programmed?

 

Also  im not sure if this is possible  but ive also heard the data can be over wrtten wit hthe same data to refresh it?  as in no UV erasing process.  ive also heard mixed answer on that lol.

 

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I'm guessing a quality EPROM could outlast a human lifespan.  I've got arcade boards from the early 80's that work fine still with many EPROMs on them.  It's a non-issue, though, as far as I'm concern

so over the years  of collecting when i first got in to test cart collecting 10 years ago i learned about eproms  and that they are not a forever solution and that eventually the data will die of bit

I'm guessing a quality EPROM could outlast a human lifespan.  I've got arcade boards from the early 80's that work fine still with many EPROMs on them.  It's a non-issue, though, as far as I'm concerned because of the existence of the internet: if a chip fails, desolder it, re-burn it, resolder it from a known good dump on the net and you're set for another 20-30-40+ years; at the end of the day, the only difference will be the quality of the replacement solder job on the board...

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So from my experience in the arcade world, it depends. Many are just fine, but then sometimes I will get a whole romset that is all corrupted. It is enough to where rom failure is one of the first thing I check for when looking at this stuff.

In my experience, I don't think I've noticed too much of a correlation between things. I have noticed that ST eproms tend to have a higher rate of failure than others.

In terms of life-span, I think the typical agreed timeframe was some 10 years, but that is dependent on the manufacturer and chip. I also feel its just a glorified guess. Check the chip's datasheet for more information. I know Atmel's new One Time Programmable Eproms supposedly garuntee 100 years, which is why I encourage using those for homebrew and repro carts.

In terms of what you can do to protect them, theres not much other than covering that window with a sticker that will not pass UV through. Don't keep exposed EPROMs in direct sunlight or whatnot. Their health is literally luck of the draw. Although, I've noticed that ones that have been rewritten and erased several times tend to not hold data as long.

That said, if you have protos or unarchived data, you should really consider dumping them and storing in some sort of online archive. Bit rot is a real thing and will corrupt each of them.

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50 minutes ago, Deadeye said:

@SNESNESCUBE64does it matter significantly if you use EEPROMs instead of EPROMs?  Or is the only difference the method of erasing?

EEPROMs sometimes have slightly different pinouts than EPROMs. For example,  a 28C256 EEPROM is not a drop in replacement for a 27c256 EPROM as it moves some pins around. You would need an adapter (which some people do with smd EEPROMs). They still have a shelf life, meaning that they can lose their data over time, but check the chip's datasheet for more information on that. Some say 10 years, some say 100.

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I’d say it depends on the chip and the manufacturer. In my experience working for 2 different major US manufacturing companies, and working with many manufactured products made in various plants within these companies, as well as third party manufacturers, I have come to understand that design life is a term that is to be taken lightly. Often times design life is “selected” for commercial and marketing reasons, rather than objectively based on scientific research. 

For pretty much all things that are basically unbreakable, manufacturers will always just say 20 years design life. Often times 20 years means in reality, it will keep going and going, but they just have to assign a term.

Often times, new products are put to the stress test. They will cycle many samples of the product, many times in a short period of time. The problem with this method is that the stress resulting from many cycles in a short period of time is often worse than the actual stress that you’d see under normal cycling condition of extended periods of time. Nonetheless, these stress tests cycling results are extrapolated to represent a number of years. They will state the design life based on statistical analysis in order to achieve a number of commercial goals, such as minimizing the amount of warranty claims, making the product look more robust compared to competitors, making the product look less robust so customers will seek frequent replacements (more revenue), etc..

The most trustworthy type of design life claim is one based on historical data. When you have a design that’s been around forever and you have a pool of actual sample specimens that have been in service and you know how long they lasted in service until failure, then you can make a legit claim. Unfortunately when there’s a drastically new product design, it’s impossible to make a guaranteed claim of designation life, because the design hasn’t had the time to be put to test. But you can make some good assumptions based off of what you have learned from previous designs.

Another point to be made, with chips, there is the design life of the physical chip itself and then there is the life of the charge. You have to make sure that you are considering the correct life.

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