Here be dragons: Preventing static damage, latchup, and metastability in the 386
29 comments
·August 17, 2025kens
Author here if you have questions about some obscure circuitry in the 386.
symaxian
Are the techniques described in the article still in use today or have they been superseded?
kens
My understanding is that modern techniques are similar, but the tradeoffs have changed as chip voltages become lower and transistors become smaller. (Admittedly, I don't know a lot about modern techniques.)
This article, from a company that designs ESD circuits, describes various modern techniques: https://monthly-pulse.com/2022/03/29/introduction-esd-protec...
cruffle_duffle
“Intel recommends an anti-static mat and a grounding wrist strap when installing a processor to avoid the danger of static electricity, also known as Electrostatic Discharge or ESD.1”
You know back when I built my computers, not once did I ever use any kind of static electricity discharge “system”. No wrist strap, no mat, no anything. And I don’t know anybody who did.
Has anybody ever actually destroyed a chip with static electricity?
(Of course it could be the climate I lived in as well)
homebrewer
Sure, I've seen enough motherboards with fried USB controllers caused by an ESD while plugging in USB memory sticks.
This is in a climate with fairly cold winters (-40°C and below isn't unheard of), so layers of wool clothing and very low humidity. It's been less of a problem recently because modern motherboards come with ESD protection, but 10-15 years ago shared computers with most USB ports no longer working were the norm.
I always touch ground before working on electronics, and often get zapped. It's a fairly common practice here AFAIK.
amock
I damaged an embedded development board by walking across a carpeted room before touching it. When I touched it I heard, felt, and saw the zap and one of the IO ports was stuck after that.
0x000xca0xfe
At one company I worked for that was making embedded devices we had a period of unusually high rate of USB hardware failures in new devices. It was not really conclusively investigated but from what I've heard it was likely a period of low humidity and the people working on assembly not wearing wrist straps consistently.
kens
Part of it is that the incentives are different for you and for the chip manufacturer. You're not going to notice if, hypothetically, one in a hundred processors gets fried from careless handling. But a 1% return rate is a huge cost to Intel that they would want to avoid.
ACCount37
I never have, and I've been in embedded for ages. So I've dealt with my fair share of chips, consumer electronics and not.
But one vital thing to understand is that a lot of those "vendor recommendations" exist to cover for rare 1% to 0.1% edge case failures.
You can put together 20 PCs, with none of them dying from ESD, and conclude that ESD "isn't a real issue". But if you have a company that puts together tens of thousands of PCs per month? Then those ugly 0.1% edge case failures WILL pop up and they WILL cost you. And if you employ enough people, one of them might be a son of Zeus with a wild Wimshurst machine hairstyle - capable of emitting two high power ESDs, complete with an audible crackle and a visible spark, per minute. So ESD straps it is.
The same applies to things like humidity control or reflow profiles for electronics. Not an issue ~99% of the time. The remaining ~1% can fuck you over in mass manufacturing, so disrespect the vendor at your own peril.
kennethrc
> Has anybody ever actually destroyed a chip with static electricity?
Piling on, but yes, you very well may have: https://www.youtube.com/watch?v=tcRqj9FhgcE
rectang
Is wonder if there's a strong correlation between whether you experience static zaps in your daily life and your propensity to fry chips with ESD.
When you fry a chip is it obvious because you experience a zap?
If so, then that would make all this "make sure you're grounded" ceremony less mysterious — because unless you feel a zap (even a tiny one) you probably haven't fried a chip, and it doesn't generally happen in environments where you don't feel zaps.
Obvious caveat: "feeling" a zap is not a precise measurement. But perhaps "zaps fry chips" is a lie which reveals a greater truth.
kens
Roughly, 3000 volts is what you can feel and 2000 volts is what can zap a chip. So you can zip chips without feeling it.
the-grump
You will fry something if you don't use anti static measures and work on enough boards.
Moisture, clothing, habits play a role so it's highly variable.
LegionMammal978
It's funny, back in an earlier job, I'd keep a board plugged into a programmer, which in turn was plugged into a USB port on my laptop. Whenever I left the restroom, my hands would be slightly wet, and touching the laptop would give me a small shock. Somehow, this shock would reset the board every time, even through the indirect connection.
I'm surprised that nothing ever actually got fried in that job. (Except for a company laptop that mysteriously bricked itself after I tried rebooting it.)
But as high-power transistors were developed, SCRs fell out of favor. In particular, once an SCR is turned on, it stays on until power is removed or reversed; this makes SCRs harder to use than transistors.
SCRs, also known as thyristors, are still widely used in very high power applications.