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ECC matters

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Re: ECC matters

#491

Post by patates »

colejohnson66 wrote: post #311
maria_weber23 wrote: post #274

Earlier quoted context omitted.

ECC memory can't eliminate the chances of these failures entirely. They can still happen. Making software resilient against bitflips in memory seems very difficult though, since it not only affects data, but also code. So in theory the behavior of software under random bit flips is well... Random. You probably would have to use multiple computers doing the same calculation and then take the answer from the quorum. I…

> You probably would have to use multiple computers doing the same calculation and then take the answer from the quorum. The Apollo missions (or was it the Space Shuttle?) did this. They had redundant computers that would work with each other to determine the “true” answer.

Forgive my ignorance, but wouldn't the computer actually reacting to the calculation (and sending a command or displaying the data) still be very vulnerable to bit-flips? Or were they displaying the results from multiple machines to humans?

Re: ECC matters

#492

Post by Faaak »

grishka wrote: post #413
nostrademons wrote: post #237

I still remember Craig Silverstein being asked what his biggest mistake at Google was and him answering "Not pushing for ECC memory." Google's initial strategy (c. 2000) around this was to save a few bucks on hardware, get non-ECC memory, and then compensate for it in software. It turns out this is a terrible idea, because if you can't count on memory being robust against cosmic rays, you also can't count on the soft…

I remember reading how someone registered some google domains with a single bit flipped, and saw actual requests coming to them.

A long time ago I did that with "CDN" domains. I bought ~10 of them (variations of fbcdn, akamai, and ytimg). I _did_ see some traffic (some hits per hour if I remember well), and many of them were from cheap handheld phones (from the user-agent).

Re: ECC matters

#493

Post by buran77 »

jandrese wrote: post #452
sitkack wrote: post #446

Earlier quoted context omitted.

The fact that ECC isn't the default across everything is a failure of human cognition and Capitalism.

I have always been angry that ECC was treated as an "enterprise" feature and increased the price way more than it should have.

It's treated as enterprise because most regular users had no realistic reason to care about it. The practical consequences of not having this on your phone or home PC are completely invisible for the vast majority of people. Because of this and the fact that in the consumer space prices matter most the situation is quite expected.

Re: ECC matters

#494

Post by buran77 »

Animats wrote: post #423
jfim wrote: post #409

Earlier quoted context omitted.

> Now if we can get ECC at the retail level You can actually, most AMD consumer chips (except the ones with integrated graphics) have ECC support, even though it's not officially supported. See this Reddit thread for more details: https://www.reddit.com/r/Amd/comments/ggmyyg/an_overview_of_...

The CPU chip can do it. Some motherboards bring out the pins to do it, but they're often called "workstation" boards and cost 2x the price of a standard desktop motherboard. ECC memory itself is overpriced. $60 for 16 GB DDR4 without ECC, $130 for 16 GB DDR4 with ECC. This is the legacy of Intel's policies.

Because if you give consumers a choice between having ECC or LEDs on otherwise identical boards with identical price, most will go for the LEDs. In reality the price isn't even the same because ECC realistically adds to the BOM (board, modules) more than LEDs do. So the price goes up with seemingly no benefit for the user.

As such features that are unattractive to the regular consumer go into workstation/enterprise offerings where the buyer understands what they're buying and why.

Re: ECC matters

#495

Post by GlitchMr »

jjeaff wrote: post #333
josefx wrote: post #121

Earlier quoted context omitted.

Just Intel fucking over security by making ECC a non feature on consumer grade hardware - wouldn't be surprised if it was just a single bit flipped in a feature mask.

Well, with as common as a bunch of people in this thread seem to think bit flips are, it should just be a matter of time until that bit gets flipped on your cpu and activates the ecc feature.

Few issues with this statement:

- That bit is not stored in RAM but rather somewhere within CPU which can have different bit flip frequency characteristics.

- Even assuming this bit can be flipped, most computers wouldn't have ECC RAM inserted because well... the CPU doesn't support it.

- And even assuming you have ECC RAM inserted, this bit flipping while your computer is running will likely lead to CPU hang considering the CPU didn't fill in error correction bits and will lead CPU to think that pretty much every single byte is corrupt.

- And all in all, even if you did manage to turn on ECC bit, it would only work until the computer gets turned off.

Re: ECC matters

#496

Post by KMag »

fulafel wrote: post #480
KMag wrote: post #453

Earlier quoted context omitted.

Anyone have any idea why there haven't been any open-source QNX clones, at least not any widely known ones? Even before their Photon MicroGUI patents expired, the clones could have used X11. I used to occasionally boot into QNX on my desktop in college. It was a very responsive and stable system. Hypervisors are, to a first approximation, microkernels with a hardware-like interface. All of this kernel bypass work bei…

There are well known open source microkernels, like Minix 3 and L4. Probably not that attractive. Why something hasn't been done is always a hard question to answer, since to succeed a lot of things have to go right, and by default none of them do. But one thing is that microkernels were more trendy in the 90s - r&d people are mostly doing things like "the cluster is the computer", unikernel, exokernel, rump kernel,…

Thinking about it a bit more, QNX clones might suffer from something akin to second system syndrome. There's a simple working design, and it likely strongly invites people to jump right to their own twist on the design before they get very far into a clone.

Re: ECC matters

#497

Post by adrian_b »

tokamak-teapot wrote: post #52
simias wrote: post #9

I used to be pretty skeptical of ECC for consumer-grade hardware, mainly because I felt that I'd always prefer cheaper/more RAM over ECC RAM even if it meant that I'd get a couple of crash every year due to rogue bitflips. For servers it's a different story, but for a desktop I'm fine dealing with some instability for better performance. But these days with the RAM density being so high and bitflipping attacks being…

Are there any Ryzen boards that support ECC and actually correct errors ?

As others have replied, all the ASRock boards where I have ever checked the specifications do support ECC and also some ASUS boards support ECC, e.g. all ASUS workstation boards.

Because ECC means Error Correcting Code, by definition, any board that claims ECC support must actually correct the errors. The ECC codes used now, with 8 extra bits for each 64 data bits, correct any 1-bit error and detect any 2-bit errors.

Very old computers (25 years old, or more) used parity instead of ECC and they just detected any 1-bit error (and any errors with an odd number of flipped bits), without being able to correct the errors.

Re: ECC matters

#498

Post by xxs »

alkonaut wrote: post #300
louwrentius wrote: post #275

Earlier quoted context omitted.

> Bit rot is just one of many threats to my data. Backups take care of that as well as other threats like theft, fire, accidental deletion. No, that's the big mistake people make: backups just backup bit-rotted data, until it is too late and the last good version is rotated out and lost forever.

I’m aware. But the risk is extremely small (and 99.9% of important data is not created on the machine but goes directly from e.g iOS camera to backup). My desktop machine is basically a gaming rig with disposable data. Hence the “performance over integrity”. I also never rotate anything out. Every version of everything is in the backups. Storage is that cheap these days.

>My desktop machine is basically a gaming rig

...unlike all the accountant machines which are just standard desktop grade ones that have invoices entered from their keyboards.

>Hence the “performance over integrity”.

If anything ECC would be better for performance, as it'd allow to clock memory higher. It's a mystery how Intel has managed to convince people ECC = enterprise/server market. The real cost of ECC is 1/8 more memory (and datatraces on the motherboard)... and if anything, virtually all intel cpus have the needed support/transistors in the memory controller, it's just desktop variants have that part fused off on purpose.

Re: ECC matters

#499

Post by DSingularity »

klodolph wrote: post #489
DSingularity wrote: post #456

Earlier quoted context omitted.

You need two alpha particles hitting the same rank of memory for failure to happen. Although super rare, even then it is still correctable. You need three before it is silent data corruption. Silent corruption is what you get with non ECC with even a single flip.

Where are you getting this from? My understanding is that these errors are predominantly caused by secondary particles from cosmic rays hitting individual memory cells, and I've never heard something so precise as "you need two alpha particles". Aren't the capacitances in modern DRAM chips extremely small?

The structure of the ECC is at the rank level. This allows for correcting single bit flips in ranks and detecting double bit flip in ranks. So when you grab a cache line each 64bit is corrected and verified.

Re: ECC matters

#500

Post by shrewduser »

klodolph wrote: post #485
shrewduser wrote: post #482

Earlier quoted context omitted.

[flagged]

Just because capitalism fails to provide something does not mean that communism would solve the problem, or that criticism of capitalism as a system is uncalled for. This is not some kind of binary capitalism/communism world we live in.

i'm just struggling to find the link between capitalism and ECC memory.
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