[sdiy-interim] EPROM Armageddon?

[Mike]

As several other people have pointed out, data retention time is quoted as a
minimum, probably top ward off lawsuits.

Thre is evidence, (and I can't find the article at the moment), thta
retention time is unfluenced by usage. The article suggested longer times if
in use. There was also a suggestion that the more recent high density ones
are subject to data erosion due to smaller gate area, (less charge per bit),
and cosmic ray bombardment

Things to do:

1) have soft copies and images, (not always the same due to several; makers
charming habit of scrambling address and/or data lines to make reverse
engineering harder). For older moulding machines I've re-burned the EPROMs,
(though I do a have a big stock of old chips due to clearing out a load of
trashed arcade machines. I'm just about out of 2532's though.)

2) Design adapters - it's quite easy to  replace, for example, 4x2716' with
a 27256, just hold down the top two address lines, and 4 --> 2 encode the
chip selects as address and chip select. I've done this routinely for
injection moulders and CNC millers. Replacing 4 cards of 2708's (Horrible 3
rail hot running things), with 1 board, in a Husky CNC lathe a while back
was the peak of this I think. I had to make a jig to read the '08's. I think
a neat idea might be a plug in EPROM holder that sits over a 24 or 28 pin
socket, with an aligned socket for a bigger EPROM, and something like a PAL
E series, with a wire wrap or similar 'switchyard'. These could be used as a
generic part, and customised for individual applications Any board layout
wizards out there?

3) Check what your micro actually was. A lot of them are not one-time may be
a problem:-  mask programmed will last as long as the chips do.

And what about the ongoing 'Chipmageddon' anyway.....gate migration is
taking out a lot of older CMOS, and am I alone in finding an icreasing
failure rate in the older 16,64, and 256 bit DRAM chips?

I don't quite have the required 'Hell Fire and Damnation' style for this. We
need preachers. "Chipmageddon is coming, prepare or be damned to eternal
silence"

Mike


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