Memory errors in consumer devices such as PCs and phones are not something you hear much about, yet they are probably one of the most common ways these machines fail.
I'll use this thread to explain how this happens, how it affects you and what you can do about it. But I'll also talk about how the industry failed to address it and how we must force them to, for the sake of sustainability. 🧵 1/17
First of all let's talk briefly about how memory works. What you have in your PC or phone is what we call dynamic random access memory. That is memory that stores bits by putting a minuscule amount of charge into vanishingly small capacitors (or not putting it in if we're storing a zero).
These capacitors continuously leak this charge, so it needs to be refreshed periodically - every few milliseconds - which is why it's called "dynamic". 2/17
Diagnosing it is hard. Windows has a memory diagnostic tool which will catch the worst offenders and is easy to use: https://www.microsoft.com/en-us/surface/do-more-with-surface/how-to-use-windows-memory-diagnostic
It's not enough though, some errors can only be caught with more extensive testing. I recommend the open-source memtest86+ (https://memtest.org/) tool or the closed source memtest86 one (https://www.memtest86.com/) 8/17
@gabrielesvelto FWIW, I wrote a "memtest.js" version that runs in the browser. I even got some bad RAM sticks from Mozilla RelEng to verify that it could detect real failures!
Live version still works, too: https://dolske.net/hacks/memtest.js/live/
@gabrielesvelto Of course there are some limitations, since JS (thankfully) doesn't have bare-metal access. But I wanted to see if periodically testing whatever chunks of memory the browser/OS gave out would work well enough.
That is, it can't say "all clear", but it can say "problems found". The idea being to eventually have the browser itself run a small background check, which over time should either detect any bad bits or give confidence that things seem OK.
@gabrielesvelto Alas it was just a side project for fun, so I set it aside after the proof-of-concept.
It seems like an interesting problem space, so I hope you get good results!
Oh, the old code: https://github.com/dolske/memtest.js
(It was also an excuse to play with the then-new asm.js, for the hot bitwise-op loops. That code is lost, but IIRC it wasn't any faster because whatever JIT we used then already did a good job.)
Gabriele Svelto [moved]
Justin Dolske