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Bit rot in EPROMs

MikeS said:
Depends on what you have available; yes, most if not all programmers can read EPROMS, but some computers also have spare sockets that you could use in a pinch if they're compatible. The later model PETs for example would be able to read a 2716 as is, and many others including PC/XTs and clones should also be able to although they might need a simple adapter.
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I have a Tandy 200 with a empty ROM-slot! I don't know what kind of ROM it support! Looking into it! Hope I don't mess up the thread!
 
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platis said:
I have a Tandy 200 with a empty ROM-slot! I don't know what kind of ROM it support! Looking into it! Hope I don't mess up the thread!
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32K x 8, bank switched, so although it'd be possible to read a 2716 it would need an adapter and be pretty tricky...

Got anything else?
 
Nothing on the moment I can recall with a empty ROM-slot! Except an old engine anlyzer, but it has a cutom OS so not so hackable! How about atari game cartridges, can you hack it and use it as a eprom reader?
 
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Just take a dump of any ROMs you can't already find images for, they can always then be reprogrammed if needed at some point.
 
Most programmers can read anything from 2716 on. Except newer parts that
have specific protocols.
2708 and 1702A require additional voltages.
If you have a computer with an additional socket for any of the 5 volt
parts, one can easily make an adapter to wire it to most any socket.
I make adapters all the time to read ROMs that have additional
selects, as is common in games and such.
As for life, a common failure in many chips is bond wires.
As for long life, I have a SIM4-01 that has 1702As that still
have their original programmed values ( yes, I've not only saved these,
I've made copies as well ). These were programmed around
1972-73 someplace.
Dwight
 
I can't tell you how happy I am to see this issue getting some attention. We all have stockpiles of equipment which will eventually fail for various reasons if not properly preserved. Unfortunately much of our old equipment isn't stable just sitting on a shelf. The EPROM issue (including PROMS, EEPROMS, flash, etc) is one that worries me a lot. I have been trying to read all ROMs that come across my desk but it really is going to take everyone doing it with all their systems and boards. I mostly collect DEC equipment and it seems like every card i look at has EPROMs on it. Beyond that even. Take your favorate CD-ROM drive that you're using. It's got an EPROM in it and will stop working soon. Some of this stuff is hard to take apart for imaging. Sometimes the ROMs are soldered to the board. I'm trying to read some DEC server roms now where they soldered the EPROM to the motherboard.
 
The idea of building adapters is a great one. I like to use wire-wrap sockets to build adapters out of because they have long leads that can be easily bent out and wires/pull up resistors soldered to as needed.
 
Absolutely. I also try to do that. Much of the programmable logic I can't read. However, for some of them that are gates only (i.e. no registers) I can sometimes build adapters to read them using an eprom reader. The inputs are the address lines and the outputs are the data lines. This isn't always possible, but it can be used with some of them.
 
Usually, no signs, just as the thread title says, "bit rot"--one day, something is suddenly wrong. In a lot of cases, the EPROM can be erased and re-burned and be fine.
 
Nope, no warning signs. Various bits in the eprom go bad and change value. Eventually enough change or an important one changes and the device stops functioning. Sometimes it only takes one bit to change to make the device fail completely. Trying to debug the problem is often very difficult if not impossible.
 
As I recall, you can reduce the voltage on an EPROM and find weak
writes. This may not be true for all manufactures. Some may require
increasing the voltage.
The speed of the read should also slow down as it is getting close
to failing.
All things that can not be easily done while in the original circuit.
Dwight
 
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