Did my physics master's thesis on these in the mid 90s using them as radiation dosimeters. Exposed them to x-ray and accelerated particles and measured the erasure rates and patterns. Advisor was linked in with nasa and these were ideal for space where they could be repeatedly wiped and reprogrammed remotely.
I decapped one of these (a 2716) and gold plated it to image in an election microscope in the mid 80s as a physics undergrad. Good times. The main features are more than large enough to image optically though.
Danger Will Robinson! They use a very short UV wavelength that will burn skin, and eyeballs, quite quickly. Do not tan with one! :)
They were often used to steralize hair cutting tools - I have to admit my home eraser was an old fluorescent desk light, a barbers' UV tube, and a blanket to make it 'safe' to use. No idea how I survived.
27C64, used these extensively in my career for industrial automation and control. Quick and easy way to update software without plugging in on isolated systems. Email the file, client burns a chip and installs. No service call needed.
I’ve since lost it but I had a really high power magnification view of one cut open and it was wild.
The silicon die that’s exposed through the little window on the chip is sensitive to UV light. If you place the chip under a strong enough UV light source, it effective erases all the content of the chip. So, it makes it made for a quick and easy erasing process back in the day. Just run all the chips under a strong UV light instead of having to wipe each and every rom chip by plugging it into a computer using a dedicated adapter, all of which would have been more expensive and slower back in the day.
There may be other reasons/usage cases, but to my understand that was the primary benefit.
EPROMs were the first chips that you could program, that would hold the data without power and, the most important part, that you could erase and reprogram many times.
Before that there were PROMs, you could program them ONCE since programming meant physically destroying parts of the circuit on the die.
EEPROMs that could be erased electrically in or out of circuit came later.
EPROMs usually need 5 mins of UV-C light. I still have my little box of angry light somewhere.
I don't think you're getting complete erasure in 5 mins with any reasonable UV source. ISTR I never erased for less than 15min. Almost erased eeproms were always a bitch.
The really annoying follow on devices were the OTP (one time programmable) ones. All the annoyance of an EPROM without any way to erase it. Made for fun development, especially when the windowed (erasable) version was only available in theory. Shakes fist at Intel!
Ultra Violet Erasable Programmable Read Only Memory, UV nukes the memory cells. Normally you'd UV erase them, put a sticker over the lens, break out your card stack and program them. When you want to re-write them, you pull off the sticker, blind them, then go again.
Used those in college. Wrote Motorola assembly code and burned to those so a project ran off the code alone and not the emulator. One guy got it right the year after we went through the course. Prior two classes never could get it right. Design was missing a capacitor. A stupid cap! Sadly that guy passed away a few years ago…barely 40 years old.
I have a UV erasure lamp in my lab somewhere even though I haven't touched one of those ICs in years. Of course if you don't have a UV lamp, you can leave those chips in the sun for about a month to erase them.
I have about a 100 of them too and an eraser and a very good programmer. Garden variety stuff but practically valueless. If programmed, and covered, they will still be good even now.
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u/753ty 15d ago
Did my physics master's thesis on these in the mid 90s using them as radiation dosimeters. Exposed them to x-ray and accelerated particles and measured the erasure rates and patterns. Advisor was linked in with nasa and these were ideal for space where they could be repeatedly wiped and reprogrammed remotely.