trough@ihuxi.UUCP (Chris Scussel) (03/28/85)
I have a repeatable example of photographic strobes causing a computer to crash. I have a microprocessor "training" board which I used for several years at our annual christmas "toy and doll night". Every time the photographer took a picture nearby, the micro would go belly-up, and have to be reset. The closest thing it had to an optical sensor was its EPROMS, and these were not erased by the flash. The best guess I had was the EMP from the discharge of the flash unit's capacitor. I'm not sure, but I think that I tried flashing a strobe near the micro while I had my hand over flashtube. It still crashed, which supports the EMP theory. Of course, none of this has any bearing on the original ESS story. Chris Scussel AT&T Bell Labs
padpowell@wateng.UUCP (PAD Powell) (03/29/85)
In article <1185@ihuxi.UUCP> trough@ihuxi.UUCP (Chris Scussel) writes: >I have a repeatable example of photographic strobes causing a computer >to crash. I have a microprocessor "training" board which I used for >several years at our annual christmas "toy and doll night". Every time >the photographer took a picture nearby, the micro would go belly-up, >and have to be reset. The closest thing it had to an optical sensor >was its EPROMS, and these were not erased by the flash. The best Ah, yes, the joys of EPROMS. A couple of years ago, some students put together a display using a single board computer system for a controller. It was meant to show how the computer worked, so the board was out in front, under a transparent cover. During the exhibit, along comes the big/little chiefs, with photographers. FLASH!!! Crash!!! Wheep!!! Alarms, etc. go off. Why? The EPROMS were uncovered, and the high light intensity caused them to malfunction. I repeated this test in the lab, and it sure worked. There are lots of explanations in the various semiconductor physics books. SOOOOO- cover up those EPROMS with black tape!!! Patrick Powell
henry@utzoo.UUCP (Henry Spencer) (03/29/85)
> I have a repeatable example of photographic strobes causing a computer > to crash. I have a microprocessor "training" board which I used for > several years at our annual christmas "toy and doll night". Every time > the photographer took a picture nearby, the micro would go belly-up, > and have to be reset. The closest thing it had to an optical sensor > was its EPROMS, and these were not erased by the flash. ... Most silicon devices are light-sensitive to some degree. In the fine print of some EPROM data sheets, you will find a warning that the window should be covered with something opaque even in the absence of UV intense enough to erase the EPROM, because normal light kicks up photoelectric currents that are strong enough to interfere with normal operation. This might account for some of the problem. -- Henry Spencer @ U of Toronto Zoology {allegra,ihnp4,linus,decvax}!utzoo!henry
rpw3@redwood.UUCP (Rob Warnock) (03/31/85)
+--------------- | I have a repeatable example of photographic strobes causing a computer | to crash... Every time the photographer took a picture nearby, the micro | would go belly-up, and have to be reset. The closest thing it had to an | optical sensor was its EPROMS, and these were not erased by the flash... | Chris Scussel | AT&T Bell Labs +--------------- The base-collector junctions of transistors tend to be light-sensitive (go look at how they build "photo-transistors"). It has been long known (but not always publicized) that the transistors in the sense amplifiers of certain EPROMs are especially light sensitive. It's not the ROM cell that's affected, so the data is not erased (unless there's enough U/V, as with naked sunlight), but read errors can happen. That's why the "paper" labels that are supplied on preprogrammed EPROMs often have an aluminum-foil layer in them, to block out light. Higher-frequency ("blue"er) light affects the EPROMS worse; hence flourescent light is worse than incandescent. I have seen (*blush* -- and been bitten by) this effect in prototypes, when engineers get busy and don't put labels over the little "windows" after erasing them. It starts getting late in the day, someone turns on the lights, and BOOM! CRASH! It can also cause EPROMs to appear bad when freshly programmed, since if you don't cover the window while programming them, PROM blasters which use "adaptive programming" can get read errors during the programming process (due to overhead lights), or during the "verify" step. Moral: Cover your EPROM windows with OPAQUE labels, except when erasing. Rob Warnock Systems Architecture Consultant UUCP: {ihnp4,ucbvax!dual}!fortune!redwood!rpw3 DDD: (415)572-2607 USPS: 510 Trinidad Lane, Foster City, CA 94404
ron@brl-tgr.ARPA (Ron Natalie <ron>) (04/01/85)
> I have a repeatable example of photographic strobes causing a computer > to crash. We have an applicon color ink jet plotter. The thing comes with a strobe light that gets synced to the units rotation so that you can adjust the convergence of the nozzles. While waiting for a plot one day, I turned the strobe on the tape drive to watch it freeze the real motion. I forgot that the tape sensors were optical. -Ron
wcs@ho95b.UUCP (Bill Stewart) (04/03/85)
The early Bell Labs BLIT terminals (in-house predecessor to the Teletype 5620) had no fan, and were occasionally subject to ovwerheating problems. The standard cure was to take the back off to get some air circulation. Well, there was this guy with a window office, who had the back of his terminal facing out. After a few weeks the incoming sunlight erased the EPROMs, and the terminal forgot what it was.... My 5620 has a fan, but it's quieter than the building A/C fan, so I've left it in (a lot of HP terminals around here seem to have their fans disconnected.)
stone@yale.ARPA (Larry Stone) (04/08/85)
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[eat flaming death, fascist media bugs |-> ]
I once had to deal with an ancient HP2100 (about the equivalent of a
PDP-11) that used paper tape for "mass storage". It had an optical tape
reader which was *very* fast, but on a sunny day we had to pull down the
shades or the sunlight streaming in would go right through the "opaque"
tape and trash the data! Fortunately, sunny days aren't much of a
problem here in New Haven.. :-)
"User-friendly is a front panel with switches & lights,"
-- Larry Stone (..!decvax!yale!stone)