systems.glitch at gmail.com
Wed Dec 13 11:18:07 CST 2017
The only "baking" I've heard about with EPROMs was *annealing* on the
original prototypes from Intel. I want to say that was before they figured
out UV erasure and were zapping the things with X-rays for erasure. You
won't be doing any EPROM annealing in a home oven :)
It's been my experience that usually defective 2708s or 2716s will fail to
program, rather than fail to erase. Be aware that some of these old EPROMs
take quite a while to erase. Newer stuff like 2764s are usually done in
around 15 minutes with my old UV eraser, but I've had to run old 2708s and
1702s for much longer, 30+ minutes usually. I think my eraser uses a 15W
lamp, for reference.
Try programming all zeros and see if it'll take. If it does, try and erase
them. If you start seeing some bits flip to one but not all of them,
increase exposure time. If you get up around an hour and you still have
zeros in some positions, the EPROM is likely bad. If you're debugging or
developing on something, I wouldn't bother messing around with potentially
bad EPROMs, especially 2716s since those are still pretty available. You
can also drop a 2816 EEPROM in there (there are other pin-compatible
EEPROMs, SEEQ had one, there may be others).
And, of course, be aware that Texas Instruments' 2716 is its own thing and
not compatible with the common 5V-only 2716s. They called their Intel 2716
compatible a 2516.
On Wed, Dec 13, 2017 at 10:33 AM, Michael Zahorik via cctalk <
cctalk at classiccmp.org> wrote:
> My homemade 8080 CPM machine used a number of 2708 and 2716 EPROMs. that
> was 40 years ago. This machine is still running and I use it, but since I
> had trouble with the EPROMs, I switched to EEPROMs. I would also be
> interested in hearing about whether or not baking would work and how to do
> the baking, exactly. I have a bunch of old EPROMs, that I figured were
> dead, but maybe not? Mike Zahorik
> From: Holm Tiffe via cctalk <cctalk at classiccmp.org>
> To: dwight via cctalk <cctalk at classiccmp.org>
> Sent: Wednesday, December 13, 2017 9:17 AM
> Subject: Re: EPROM baking
> Hmm..I've read about that baking in conjunction with 1702A too..but
> don't remember the source of that discussion. I know that ppl suggested
> it for proms that would'nt program correctly...
> dwight via cctalk wrote:
> > When I was at Intel, years ago, I recall the baking was only to repair
> the retention of the EPROMs. It was not to fix random failures.
> > It sounds like your EPROMs have various failures that wouldn't be helped
> by baking.
> > Each time the EPROM is programmed, there is a slight increase in the
> leakage of the floating gate. This was typical after thousands of
> program/erase cycles. Baking them repaired the damage to the insulating
> layer that was damaged.
> > Dwight
> > ________________________________
> > From: cctalk <cctalk-bounces at classiccmp.org> on behalf of william
> degnan via cctalk <cctalk at classiccmp.org>
> > Sent: Wednesday, December 13, 2017 6:18:16 AM
> > To: Mark G Thomas; General Discussion: On-Topic and Off-Topic Posts
> > Subject: Re: EPROM baking
> > On Wed, Dec 13, 2017 at 9:08 AM, Mark G Thomas via cctalk <
> > cctalk at classiccmp.org> wrote:
> > > Hi,
> > >
> > > I am working on several projects requiring 2708 and 2716 EPROMs, and
> > > am finding some of my chips will not erase, and some will not take
> > > a program. I've also learned more in the past week than I wanted
> > > to know about repairing Data-I/O 29a/b programmers.
> > >
> > > I vaguely remember in the 1990s baking such EPROMs in the oven, but
> > > I do not remember temperature or time. I was surprised that Google
> > > didn't turn up anything useful with this info.
> > >
> > > I'm sure someone here will have some notes on EPROM baking.
> > >
> > > Mark
> > >
> > >
> > >
> > Mark,
> > If this is an issue about reviving bad eproms? I assume you have tried
> > regular stuff.
> > What process are you using now to erase 2708/16's? I have a simple
> > unit and it seems to always work. Some eproms go bad but I never have
> > issues with erasing them. My point is that maybe you need a better prom
> > eraser unit. I would avoid baking them until you have exhausted other
> > options. Not sure what others think. This topic has come up before
> > about putting them outside and all that. The erasers are all over ebay,
> > and the hardware store is full of the correct types of lighting, why not
> > make a box that will do the job? I assume there is more to it that
> > simply erasing them.
> > Bill
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