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Comment by DeathArrow | Hacker News Reader

>I’ve found by reading papers about it that 1 bit error per 4 GB RAM per 3

So for my 64GB of RAM I get 2 bytes worth of errors / day. And a few hundred for 2 or 3 months since I didn't restart my PC.

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This could easily be true, and easily have zero impact on anything you are doing.

Memory can be assigned to all sorts of things so the impact of a single bit change will depend entirely on what that memory is being used for at that moment.

For example, I load a program into memory, but I'm not running all of the code in that program all the time. Let's say the program includes code for exporting a list to excel, but that's a feature I never use.

Or it has a procedure which uses a local variable as a loop counter. Outside the confines of that loop the variable is meaningless.

Plus its unlikely you are even nominally using all 64g at the same time. The errors might all be happening in unused ram.

Even if it flips actual data, it may end up being no more than a typo in a document.

So yes, a single bit in 4gb might flip from time to time. But the probability of the flip being "meaningful" is less than 1.

IMHO a typo in a document is a serious error that we should put substantial effort into preventing.

There are even worse potential outcomes:

* A single bit error in a stream of compressed or encrypted data stream that renders the stream unreadable.

* A permissions check being yes instead of no.

* Backups being silently corrupted

While a typo can be significant, statistically speaking it almost certainly isn't. Equally I'm not saying that all bit flips are inconsequential. I'm saying that most bit flips likely go either completely undetected, or have meaningless consequences.

Saying that say 1 bit per 4Gb will flip every day is a long way from saying that a _significant_ (or even detectable) bit flip will happen every day (per 4Gb). From a simple feel for "what memory is used for", coupled with "how much of the ram is actually used" makes me suspect that it's a very low probability of it being an issue.

Which makes the parent comment, about 1600 bits of data being flipped since the machine last rebooted [1] being both "true" and likely "meaningless".

[1] I'm not sure what rebooting has to do with anything though.

I get what you're saying but on the other hand isn't bit-flipping that results in typos or crashes something that is so beneath 2022?

Like isn't this the kind of thing that Turing and Zuse had to deal with?

And if it isn't, when is it a problem that we will finally and absolutely excise?

Is it more of a 2030 thing? 2040?

With more and more miniaturization such stochastical behaviour becomes more and more prevalent. Same with higher and higher speed interconnects. Forward error correction is standard on e.g. NAND flash, VRAM for GPUs and being adopted by faster Ethernet standards. It's mostly just the consumer dram market that doesn't have robust error correction.

Or it can have catastrophic effects.

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