refreshing eproms?

The danger of Bit Rot.

never heard of this problem before, but did some reading, 10-35 years is est life of EPROM data... yikes, weve got a lot of machines pushing 20-30!

I have a Needhams electronics burner, it wont program a chip that isnt erased...anyone know of a burner that will attempt to overwrite a chip without checking erase first? If I understand the degradation process right, reading/reburning a functional chip with its exact current program(and storing the image) without erasing would be faster than erasing, and get another 10-35 years... verify is automatic on most burners, however the auto speed-up attempts would need disabled...on needhams, the default burn is kinda slow, optimized it goes faster and faster till it misses a bit, then slows down and rewrites again...it cuts time dramatically, but wouldnt work for a reburn as there would never be any errors :)

I've only ever seen like 2 known for sure eprom failures, but got a feeling the tip of the iceberg is starting to show. I have my ladders backed up, but really- every system rom, servo rom, spindle rom, graphics rom probably ought to be saved somewhere after reading this stuff...

thoughts?

The best thing to do is simply buy one of the cheap Winpro programmers, and read all the chips saving them to a binary file. And then burn a set of backups as spare. If they are plain eproms you should have no trouble as there's no protection fuse for these chip.

cheers,
Ian

If you own an old CNC machine then yes back up all the EPROMs.
If not then it'll die one day but it's not your problem ;-)
EPROMs are solid stable devices. The PCBs will surely die before the EPROMs.

I have 8 programmers. Needhams programmers are crap ;-)

You can't write to an EPROM unless it is erased first. You can buy a cheap UV EPROM eraser on ebay. That is what the quartz window is for and why a sticker covers the window to prevent erasure from extended exposure to sunlight.

Or you can buy EEPROMs. Instead of the first number being 27 they are 28. So for example if your EPROM is 27C64 you buy 28C64. They are really common. Just check ebay. EEPROM means Electrically Erasable Programmable Read Only Memory. The programmer can erase it and program it in one step.

Also note old EPROMs are unreliable. It is better to buy new chips than re-program old ones.
They are as cheap as chips :-D

I've had uv eproms that got flakey. Reading them at reduced temperature, to a file and repeating a higher temperature should ALWAYS read the same.
Surprise surprise!! Not always. Usually read better when cooled if they are getting near the end of life. The charges on the bits, internally stored on capacitors slowly leak away, or possibly get zapped by cosmic rays, (who really knows).
After 10 years I have found plenty of unreliable ones in all sorts of equipment.

There were also specials made -- apple computers did it -- crude copy protection -- that had a swapped chip select line for an address line. Programmer would read them supposed OK (but only half read really) then you programmed a normal chip. Checksum matched but they didn't work. (wtf !!)

Buy new ones and reprogram.
I use my UV eraser for curing epoxy these days. hahaha