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ECC and DDR5

etbe.coker.com.au

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Re: ECC and DDR5

#121

Post by etbe »

projektfu wrote: post #12
AlexandrB wrote: post #2

Interesting article, and I agree that ECC needs to be more widely available. But I think this is a major overreach: > We need ECC RAM to be more widely used. Ideally we would have some government action to force this given the ongoing cost to society in corrupted data and lost time due to RAM hardware errors. I think that at minimum we need sufficient taxes on non-ECC RAM (and EC4 RAM for DDR5) to make it more expens…

Important data should probably be worked on and stored with error-correcting codes, in addition to the hardware-provided ones. The Btrfs mention in TFA suggests that maintaining integrity of the Btrfs metadata is not considered part of the job description of Btrfs, but perhaps it should be.

BTRFS has checksums on all metadata. It isn't designed to cope with bad RAM but has been shown to be somewhat resistant to it to the degree that BTRFS developers can recognise symptoms in problem reports.

Whether a filesystem could be designed to operate in the face of random memory changes would be an interesting computer science research topic. But for getting working systems having RAM just not fail is a better option.

Re: ECC and DDR5

#122

Post by etbe »

ck2 wrote: post #7

16GB ECC DDR5 was $50 early 2025 it is now $500 when the AI/datacenter bubble finally bursts we are going to have some amazing hardware deals

I'm planning some RAM purchases for the end of this year, I expect the crash to happen in a few months.

Re: ECC and DDR5

#123

Post by etbe »

lightedman wrote: post #44
adrian_b wrote: post #29

Earlier quoted context omitted.

This would be a consumer protection law like any other such law. Forcing the vendors to sell only products that do what they are advertised cannot be considered in any way as "forcing unnecessary things upon people". Any computer without ECC memory is a computer that does not compute from time to time and you have no idea when that happens. Originally, any IBM PC or compatible had memory error detection. All this pro…

"All this problem of the computers without ECC memory has been created by some evil Intel employees, who have conceived around 1994 a scheme for market segmentation between "Pentium" and "Pentium Pro"." I hate to break it to you but the computer I had in the 80s didn't come with ECC. Non-ECC computing was a thing WELL BEFORE Intel tried to think of market segmentation. Revisionist history is not welcomed here.

The original IBM PC/XT had parity RAM. In the early PC/XT and PC/AT clones you had banks of 9 DIP sockets for memory chips with the 9th being for parity.

The DDR4 ECC RAM has 72 bits total and 64bits of data which means the same 9/8 ratio of data storage to usable data as the original PC/XT.

The Z80 and 6502 based computers in the 80s typically didn't have parity RAM. The Amiga and Macintosh were higher performance systems in the 80s which also didn't have parity RAM.

We could and should have gone straight from parity RAM to ECC RAM for everything.

Re: ECC and DDR5

#124

Post by etbe »

CamperBob2 wrote: post #81
_factor wrote: post #30

Earlier quoted context omitted.

Right, the opinion shifting to the people being unworthy of uncorrupted data unless they’re wealthy enough to pay the artificial extortion price for integrity.

What you're actually saying is that I shouldn't be allowed to determine what kind of RAM my application needs. Instead, you are saying that someone with a gun should dictate this choice to me. That's what we mean when we say that people with your point of view are promoting nanny-statism. It amounts to infantilization of adult consumers and subsequent disempowerment. Occasionally such legislation can be justified, as…

How do YOU propose doing this when most computer "experts" have never used ECC RAM and when it's only available in high end specialist systems that aren't on sale in regular computer stores?

I think my knowledge of the topic is pretty good but I learned from this discussion that almost all AMD CPUs support ECC RAM and you apparently just need a motherboard to match. When accompanying people who were buying "gamer" PCs (after they rejected my recommendation for a second hand workstation grade computer with ECC RAM) I never witnessed store staff saying "hey you could get a motherboard with ECC support".

Re: ECC and DDR5

#125

Post by etbe »

jcalvinowens wrote: post #15

> One thing that concerns me is the possibility of on-die ECC interacting with ECC on the motherboard and reducing it’s effectiveness DDR5 on-die ECC detects and corrects one-bit errors. It cannot detect two-bit errors, so it will miscorrect some of them into three-bit errors. My understanding is that the on-die error correction scheme is specifically specially designed such that the resulting three-bit errors are ma…

The people designing RAM and motherboards and the people working at JEDEC will of course know more about these things than almost everyone who reads hacker news. But I'd still prefer not to just blindly trust that they do the best things for us and have some documentation available.

Is anyone here good at navigating patent records? I would be surprised if there isn't something to be revealed in a patent but I don't know how to find it.

Re: ECC and DDR5

#126

Post by CamperBob2 »

etbe wrote: post #124
CamperBob2 wrote: post #81

Earlier quoted context omitted.

What you're actually saying is that I shouldn't be allowed to determine what kind of RAM my application needs. Instead, you are saying that someone with a gun should dictate this choice to me. That's what we mean when we say that people with your point of view are promoting nanny-statism. It amounts to infantilization of adult consumers and subsequent disempowerment. Occasionally such legislation can be justified, as…

How do YOU propose doing this when most computer "experts" have never used ECC RAM and when it's only available in high end specialist systems that aren't on sale in regular computer stores? I think my knowledge of the topic is pretty good but I learned from this discussion that almost all AMD CPUs support ECC RAM and you apparently just need a motherboard to match. When accompanying people who were buying "gamer" PC…

It's simply none of my business whether or not someone does the homework to understand what kind of RAM they should buy. I bothered to inform myself; they can, too.

Re: ECC and DDR5

#127

Post by _factor »

CamperBob2 wrote: post #126
etbe wrote: post #124

Earlier quoted context omitted.

How do YOU propose doing this when most computer "experts" have never used ECC RAM and when it's only available in high end specialist systems that aren't on sale in regular computer stores? I think my knowledge of the topic is pretty good but I learned from this discussion that almost all AMD CPUs support ECC RAM and you apparently just need a motherboard to match. When accompanying people who were buying "gamer" PC…

It's simply none of my business whether or not someone does the homework to understand what kind of RAM they should buy. I bothered to inform myself; they can, too.

Next up. CPUs that will spit out the wrong calculations 1/1M times. You’ll have to pay more for the enterprise version to get uncorrupted processing. The spare traces cost 5 cents, but we can charge 20% more for the privilege instead.

Just because you can allow it, doesn’t mean you should. I don’t want to live in a world where you need a PhD to avoid being scammed by increasingly sophisticated ploys. Data isn’t free anymore and the right questions are becoming harder to ask.

Re: ECC and DDR5

#128

Post by burnt-resistor »

ECC end-to-end means carrying sufficient parity along the whole way including at-rest (memory and storage hierarchy), links, buffering, and computation. Skipping ECC in transposer/buffering/bus circuitry creates a source of silent errors. Silent errors are way, way too prevalent across billions of users and the vast majority never understand the source of such malfunctions or know they happen.

Re: ECC and DDR5

#129

Post by BobbyTables2 »

cobbzilla wrote: post #32
jcalvinowens wrote: post #15

> One thing that concerns me is the possibility of on-die ECC interacting with ECC on the motherboard and reducing it’s effectiveness DDR5 on-die ECC detects and corrects one-bit errors. It cannot detect two-bit errors, so it will miscorrect some of them into three-bit errors. My understanding is that the on-die error correction scheme is specifically specially designed such that the resulting three-bit errors are ma…

Very good point. It’s nontrivial but not impossible to determine this, I am very curious! One nightmare scenario is a 3-bit error being detected as a correctable 1-bit error upstream, resulting in data corruption. I agree it’d be really nice to know that could never happen!

What about rowhammer attacks ?

Wonder if they could be used to introduce “correctable” errors…

Re: ECC and DDR5

#130

Post by CamperBob2 »

_factor wrote: post #127
CamperBob2 wrote: post #126

Earlier quoted context omitted.

It's simply none of my business whether or not someone does the homework to understand what kind of RAM they should buy. I bothered to inform myself; they can, too.

Next up. CPUs that will spit out the wrong calculations 1/1M times. You’ll have to pay more for the enterprise version to get uncorrupted processing. The spare traces cost 5 cents, but we can charge 20% more for the privilege instead. Just because you can allow it, doesn’t mean you should. I don’t want to live in a world where you need a PhD to avoid being scammed by increasingly sophisticated ploys. Data isn’t free…

Data isn’t free anymore and the right questions are becoming harder to ask.

Ridiculous. Access to knowledge has never been as widely and freely available as it is now (no thanks to the nanny-statists.)

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