ECC and DDR5

https://etbe.coker.com.au/2026/07/19/ecc-ddr5/

by zdw • 3 days ago

143 151 3 days ago

etbe.coker.com.au

AlexandrB• 2 days ago

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 expensive when bought new than ECC RAM.

ECC RAM is not needed for every application and mandating it for every gaming rig and machine used to run Chrome will just increase prices unnecessarily. 99% of the time it's also not a "cost to society" but a cost to whoever owns/uses that machine. If they want to eat that cost, it should be up to them.

graemep4• 2 days ago

ECC RAM is not needed for every application and mandating it for every gaming rig and machine used to run Chrome will just increase prices unnecessarily.

The price increase will be very small if manufacturers are no longer able to segment the market to make a higher margin on those who need it. No one wants even games or web browsers to crash randomly.

If they want to eat that cost, it should be up to them.

They need to be given the choice. Most people do not know they even have the choice, and they are not offered it at a reasonable price.

A cost to people in general is a cost to society.

procaryote• 2 days ago

Without quantifying the cost to society that someone's web-browser crashes sometimes, it's hard to make a rational case that this issue is so dire that it needs specific regulation.

I'm not sure making it illegal to sell consumer grade hardware is the boon for the people you imagine

gruez• 2 days ago

The price increase will be very small if manufacturers are no longer able to segment the market to make a higher margin on those who need it.

AMD doesn't have this segmentation. Where's the hoard of people building systems with ECC ram? At best you have a few people on HN saying they're doing it, but in practice nobody actually does it.

projektfu• 2 days ago

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.

etbe22• 2 days ago

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.

nahuel0x• 2 days ago

Something important not discussed here is that you need not only error correction (when possible) but also error reporting, so you can know you RAM is failing. Sadly, is not possible to get DDR5 on-die ECC error counts reported to the OS. Alternative solution, use IBECC with DDR5, where the CPU reserves a portion of the RAM for parity bits and does the check / reporting.

inigyou5• 2 days ago

My Linux installation came with an AMD MCE driver that reports them to dmesg. It logs a few corrected errors a day.

rubatuga• 2 days ago

Isn't that a lot? I see them only when heavily over clocking .

adrian_b15• 2 days ago

A few errors per day seems much too frequent, unless you live at a high altitude.

Normal good DIMMs, at least when new, should not have errors more frequently than one error per many months.

Frequent errors may appear with memories that are not seated well in their sockets, or which are old, at least several years old.

Frequent errors may also be caused by more general computer problems, like a bad power supply unit.

loeg• 2 days ago

Check if those are all coming from DIMMs, as opposed to other subsystems (on-die caches).

cyanmagenta2• 2 days ago

The problem I have with ECC discussions is that it’s always anecdotal. There is one Google study finding memory flips with some probability in their datacenters, but it was awhile ago. Everyone repeats the statement DDR5 on-die ECC isn’t a replacement for regular ECC, but nobody ever shows data on DDR5 bitflips. That’s not a knock on this article per se, but it’d be nice to have actual data here.

phkahler• 2 days ago

> Everyone repeats the statement DDR5 on-die ECC isn’t a replacement for regular ECC, but nobody ever shows data on DDR5 bitflips.

That's because the on-die ECC cannot detect errors in the transmission of data from the DIMMs to the CPU. It seems like on-die ECC is meant to "hide" some level of errors to make less reliable RAM chips appear good. I have no idea if that's a reasonable way to do it, but it seems like it could be misused. Like TFA suggests, we need to know how the two levels of ECC interact.

cyanmagenta2• 2 days ago

Right. Everyone agrees that real ECC is more robust, and production servers of course run it. But it seems to me that if most RAM bitflips are in the module itself (rather than in transmission to CPU), then on-die ECC could in theory make the probability of a bitflip in practice so low that for things like home servers it isn’t worth the price premium for real ECC. But without data on this, everyone is just speculating.

adrian_b15• 2 days ago

As TFA says, it is very likely that the hyperscalers continue to make studies about DRAM reliability in their servers, but they do not publish them, either because they believe that such data could be useful for competitors, or, more likely, they might have NDAs with the memory vendors.

When you do not own a great number of servers, you cannot provide anything else except anecdotal evidence.

Because the vast majority of PCs do not have ECC memory, even the companies that have a great number of PCs have no idea about the reliability of the memory used in those PCs, because it is very difficult to distinguish memory defects from the huge number of software bugs.

Moreover, the frequency of memory errors is proportional with the amount of memory you have, so those with tiny amounts of memory, like 8 GB, are much less likely to encounter memory errors than those who have 32 GB or 64 GB of DRAM in their PCs.

I have tried to always use ECC memory in my computers, whenever possible. Even my laptop is an older Dell Precision, with ECC memory.

But I can also offer only anecdotal testimony.

I have also seen cases like that mentioned in TFA, where the existence of ECC allowed to discover that some modules were not seated well in their sockets, so reseating them prevented the reappearance of errors.

I have also seen a case when a laptop was not used for a long time and it was stored in a rather humid place, so the contacts in the SODIMM sockets had oxidized, which resulted in frequent memory errors. Scrubbing vigorously the contacts and reinserting the memory modules solved the problem.

I have also seen many cases where certain memory modules degraded after many years of use, e.g. 5 or more years of 24/7 use, and they began to have frequent errors, e.g. multiple errors per day, even if when they were new the error rate could have been of one error per year or even less.

In such cases ECC was extremely useful, because the DIMM that had become worn out could be identified and replaced and the server could work fine some more years.

doctorpangloss2• 2 days ago

i have years and terabytes of ECC DDR4 and DDR5 memories, UDIMM and RDIMM, with edac enabled all this time, and i have literally never once observed a single error correction. however, (1) i built all these computers myself (2) the servers are located on the middle floor a thick, concrete multi-story warehouse-to-office conversion. as others have said, on a correctly built computer, the source of bit flips is cosmic radiation, and there is a lot of mass between these machines and the sky.

SnowflakeOnIce• 2 days ago

It's not just cosmic radiation or improperly built computers that result in bit flips. Row hammer is a thing :)

Havoc2• 2 days ago

Got ECC udimm for my ddr4 server and was surprised to see it picking up errors occasionally (once every couple months). Likely from a weakness in one of the sticks. This far it’s always corrected it though so opted to keep them anyway (nobody wants to be minus 32gb in these trying memory times)

With normal sticks I’d not have know that there is a potential issue.

zargon6• 2 days ago

You should be able to get the stick replaced under warranty. Every memory manufacturer I have ever seen has a lifetime warranty. As long as you RMA it before replacements become unavailable.

Aurornis• 2 days ago

There should not be errors during normal use at rated speeds.

With non-ECC RAM running a memory test and getting any errors means it’s not stable. The memory tests run at maximum bandwidth constantly so a few days of full bandwidth memory testing might produce as many transmissions as your months of regular server use. Seeing bit errors (even if corrected) means something is not right.

The ECC can correct it for a while but I would want to RMA that stick if it’s in warranty.

Havoc2• 2 days ago

Alas this is white label mem off eBay and fair bit of time has elapsed so not confident exchange would work. Minor miracle the ECC works at all given that

At some point I should try running it at slightly lower speed i guess. It’s very hard to troubleshoot something that only happens every month or two though

Never seen it fail a memtest but I can see it in the ECC stats since those cover weeks/months.

inigyou5• 1 day ago

That was true in DDR4 but I understand DDR5 has pushed density so far that you do get errors in normal modules - like early LCD panels that were expected to have a few stuck pixels - and therefore ECC should really be mandatory.

wpm• 2 days ago

Depending on your server's CPU sockets, reseating the CPU might help if they were ever swapped before (esp if you got the server used). I have a marginally bad RAM slot on one of my Supermicro X11 boards because my dumb ass dropped the CPU into the socket and bent a few pins. I bent them back, but you can only do so much and the furthest RAM slot won't work without throwing errors daily if I run it at 2400MHz.

etbe22• 2 days ago

I have a HP Z640 that only has 3/4 DIMM slots working. Reseating the CPU didn't help and the same CPU works perfectly in another Z640. I never found out the cause. It was sold as "unknown condition for parts" so $50 for a server that works perfectly apart from one DIMM slot is still a good deal.

ck2• 2 days ago

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

bartleeanderson• 2 days ago

I had a conversation with chatgpt about that very thing, whether it was a bubble or not and how the big players could absorb the cost and where it would all land and the interesting thing was if China gets its foothold and grabs enough share because the prices are too high even being subsidized, that could cause real trouble. But the point was its not a bubble in the conventional sense. Have your own conversation about that with an AI.

HDBaseT• 2 days ago

I'd rather just have the conversation here. I don't need some hallucinated random seed response to tell me what China can and cannot do.

Of course an AI is going to tell you AI isn't a bubble.

etbe22• 2 days ago

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

warmwaffles• 1 day ago

When that bubble does finally burst, you won't be able to afford those amazing hardware deals due to the economy being in the tank for a while.

lightedman2• 2 days ago

"Ideally we would have some government action to force this given the ongoing cost to society in corrupted data"

Why is it so often Australia with the "We must force unnecessary things upon people" attitude?

Xirdus• 2 days ago

Because despite geographical location, Australia is a western country, and all western countries are like that.

gleenn• 2 days ago

That particular quote did stand out to me. I think the counter claim is that if everyone uses software everywhere for everything, there is a very real societal cost for damaged data and if it's hard to detect then there is no way to prevent or measure harm. I think the "invisible hand" free market is showing some serious strain in modern times. People stopped using leaded-gas because it was causing measurable decreases in IQ for generations. I don't care how much you want to save a few dollars if it harms a lot of people and is difficult to measure. Everything else seems like a race to the bottom price so pushing the market in this manner doesn't bother me in the least. If you are running a server with others' data at stake, it seems like an obvious benefit for society on the whole to address the problem rather than serve some cheap datacenter operators.

some_random5• 2 days ago

I think it's a pattern that reinforces itself, as a nanny state develops it's opinion of it's people worsens and it's more willing to use force to compel them.

_factor2• 2 days ago

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.

inigyou5• 2 days ago

How is it unnecessary. Australia has tons of laws about faulty products. All developed countries do

adrian_b15• 2 days ago

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 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".

So they removed memory error detection support from the Pentium chipsets (Intel Triton), so that this would remain a marketing feature exclusive to the "Pro" Intel products.

Obviously the removal of this feature from "consumer" products was done without any price reduction, which made happy also the memory vendors, because this trick increased their profits.

So in the next years this market segmentation method became the "standard" business practice, preying on the naivety of most computer users.

A consumer protection law should force that any computer or motherboard must support ECC, which adds a completely negligible cost.

The end users may buy non-ECC modules, if they choose so, but non-ECC modules should be sold like cigarettes, with a visible advertisement that using such modules may cause unpredictable errors in your computer.

flaunf2213• 2 days ago

Any computer without ECC memory is a computer that does not compute from time to time

So are the computers with ECC memory. It's not an absolute protection either.

lightedman2• 2 days ago

"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.

jcalvinowens• 2 days ago

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 mathematically guaranteed to be detected as uncorrectable two-bit errors by a standard full system-level ECC running on top of the on-die ECC. But I've never found a real authoritative reference that directly says that.

cobbzilla• 2 days ago

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!

BobbyTables2• 2 days ago

What about rowhammer attacks ?

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

etbe22• 2 days ago

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.

exabrial• 2 days ago

We need ECC RAM to be more widely used. Ideally we would have some government action to force this given the ongoing cost....

The rest of this article is great. This, however, is absolute garbage and nonsense. The last thing you want is more regulations and "government certified systems". Take a look at the bullshit with age verification bills and operating systems.

mihular• 2 days ago

We need any RAM at this point.

wmf3• 2 days ago

"This, however, is absolute garbage and nonsense. The last thing you want is more regulations and government certified systems." — the guy who designed the Ford Pinto

jmb993• 2 days ago

How is “all RAM sold in consumer PCs must be registered ECC” equivalent to age verification laws? I’m not saying I agree with the premise but that is a bit of a leap

snvzz• 2 days ago

I run a 9800x3d with 96GB ECC (2x 48GB DDR5-5800).

It was a pain to select a compatible board and source the RAM but glad I did, in June 2024... the RAM prices went up immediately after.

non-ECC should be a kernel taint in Linux. Newer versions of Windows (12?) should also refuse to boot without ECC. It should be mandatory in DDR6. The insanity must end.

etbe22• 2 days ago

Yes a kernel taint is a really good idea!

nu11ptr• 2 days ago

I've always thought it odd that we don't use ECC as a standard on all computers. I think people really downplay the impact of memory issues. They can be devastating, especially over time. They will slowly corrupt your file system, documents, binary files, code, everything. You notice when things like your compressed files start giving CRC/checksum errors or your downloads don't match SHA-512. You are then left with this "icky" feeling. What parts of your work are compromised? Obviously this is far worse with things like binary files and structures than those built on readable text. I have normally just rebuilt my system from scratch in these instances (after fixing the issue of course), but not all our files are replaceable, and you forever and always might have corrupted files you are unaware of that got written during this time. You might not find them until years later.

auspiv• 2 days ago

This is/was classic market segmentation. Want ECC? Pay up for Xeon (server/workstation CPU)

scheme2714• 2 days ago

AMD has historically supported ECC on all it's chips. That's changed in the last gen or two where some of the lower end APUs don't support ECC but the Pro APUs do and all the ryzen stuff (5, 7, 9) support ECC if you get a motherboard that supports it.

zerof1l• 2 days ago

It's very important IMO that the ECC failures get reported and logged. The DDR5 on-die correction is not true ECC; the correction happens silently and is not reported or logged.

I have DDR4 ECC memory on my home server. Last week I got a crash... logged into my BMC and saw that one of the modules had "uncorrectable ECC". Then I looked over the logs and saw about 200 or so errors for the exact same module but "correctable ECC". They would happen over a short period of time followed by 4 months of no issues. Thanks to ECC and logging it was quick and easy to catch the issue right on the first occurrence, no data corruption. I have 4 modules in total, and only this one was having issues, so clearly a hardware fault.

Now imagine it was a regular non-ECC memory. There won’t be any crashes due to uncorrectable ECC; another 3 or more years would pass before corruption would become frequent enough for the issue to be noticed. At that point, there would be hundreds of corrupted files.

flaunf2213• 2 days ago

You notice when things like your compressed files start giving CRC/checksum errors or your downloads don't match SHA-512.

And 9 times out of 10 (probably much more) it will be faulty storage, not RAM.

I'd say you are way overestimating impact of no-ECC.

piguin• 2 days ago

You need the ECC RAM for your filesystem with integrity only then can you be confident you aren't going to be familiar with a concept like this happening 9 or 10 times.

creatonez2• 2 days ago

...No? Faulty storage will almost always show up as I/O errors, modern storage generally doesn't want to send a block of data to the CPU if there is an error in it. If your bits are flipping, chances are it's RAM and not storage. Your storage already has ECC.

Some crappy flash drives might not do this, though. Seems to behave like a floppy disk at times.

TacticalCoder• 2 days ago

I think people really downplay the impact of memory issues.

I don't think so. I've got my important data backed up on offline HDDs and SSDs and my most important data lives on a RAID system (ZFS) on a Xeon with ECC RAM but...

... there are simply a huge lot of checks everywhere making it so that bit flips on non ECC systems simply aren't that serious.

We live in a world of checksums and retries at every layer and distributed systems that are just about everywhere.

I went on for decades without ECC memory and nothing bad happened. Yes, I had the occasional bitflips. I did found out faulty mem using memtest (or weirder stuff, like some RAM stick identical to the other three, same chip everywhere, same sticker: but reported by memstick as being some other mem).

But I don't think that the "one bitflip cascading into corruption of your life's data" is something necessary to freak about.

It's not happening. Never happened to anyone.

If you (or other) are really concerned, you can use my scheme:

    - dsc09874.jpg

becomes:

    - dsc09874-b3-73b0835221.jpg

which means "that file's Blake3 checksum begins with 73b0835221" (use something else than Blake3 if so desired).

About 1/3rd of all my files are "tagged" this way, directly in the filename: this survive different medium and different OSes.

I then have my custom rsync backuping script doing a dry-run and warning me in a "stop the world!" fashion if it detects a bogus checksum (either on the source or on the dest: during the dry-run any modification to a file with a checksum is verified and any checksum mismatch means "stop the world").

I then also have, in addition to my custom backuping script, another script that allows me to verify either all files with that naming convention or a percentage I pick of those files (so basically some random sampling).

It's not mutually exclusive with ZFS / a system with ECC RAM.

but not all our files are replaceable, and you forever and always might have corrupted files you are unaware of that got written during this time

I hear you but... How much do you really need, years later, a file that you haven't needed for years? That one file is unlikely to be a big loss.

Now I'm not saying you're wrong: I ended up with my naming scheme (appending a partial cryptographic hash to the filename) after finding a series of about 20 pictures that were corrupted. And on all the backups I first checked, they were also corrupted. I ended up finding a very old data CD on which that series of .jpg files were fine. And I decided "never again, I want such SNAFU to be detected in the future".

But truth is: with 40 000 pictures, life without those 20 pictures would still be fine.

inigyou5• 1 day ago

This fact comes mostly down to Intel choosing to use ECC support for market segmentation. If you care about your data, you buy the server chips that cost double what the desktop chips with ECC support lasered out cost.

monster_truck2• 2 days ago

This is not a very good post.

Claiming that every issue you've experienced is from seating errors? Come on man, at least deliberately reproduce that scenario once. I've tortured motherboards for fun and never managed that on purpose. We did pry every cap off of an old K6 board while it was on and... it just kept running. It didn't come back after we turned it off

The amount of time it takes to reseat memory, even if the case is already open and ready, is also more than enough time for it to cool back down.

If you have decent memory running at what it's rated for and you're seeing more than a couple per year, good odds are it's getting too hot or the load line calibration is not aggressive enough.

E: I have never, and I mean literally never, seen age or abuse play a factor.

etbe22• 2 days ago

I can only report what I have seen. Feel free to write your own blog post reporting what you have seen.

monster_truck2• 21 hours ago

I do, often, and respect the time of my readers enough to verify my claims instead of presenting anecdoes as fact.

sandreas• 2 days ago

One thing I also did not know until recently was that there actually is ECC unified memory.

I noticed the difference because in a Hardware forum someone wrote that the framework desktop does not have ECC while an HP G2 Workstation also featuring the Ryzen 395 Max but in the ECC supporting variant paying a premium of +600 bucks.

hamilyon2• 2 days ago

Does encrypted memory give ECC-like detection benefit, along with rowhammer protection, for cheaper cost (only additional computation), and 100% reliable?

howard941• 2 days ago

ECC is essentially mandatory for ZFS. Assuming that is you prefer your data uncorrupted.

scheme2714• 2 days ago

It's preferred but not having it still works if you're willing to leave some potential avenues for errors to get in. However, it's not like not having ECC is a recipe for a corrupted FS.

throwaway270925• 2 days ago

ECC is essentially mandatory for ZFS

Please stop repeating this old myth, it is - and always has been - BS and needs to die.

See for example: https://kldload.com/zfs-wiki/myths

hangonhn• 2 days ago

"I have used more than a few systems with ECC UDIMMs and I recommend avoiding them if convenient as ECC UDIMMs are expensive on the second hand market while ECC RDIMMs can get very cheap."

Boy did I learn that the hard way. I found an ASRock server motherboard that fit my needs for a NAS perfectly. I just assumed all ECC memory were registered so I didn't even bother to check. I had already put everything together minus the memory. I had actually purchased the memory and had to return them because they were RDIMMs and get the ECC UDIMMs for quite a bit more. Luckily this was just before the AI induced price spike.

etbe22• 2 days ago

A very large portion of people who go from working on consumer grade systems to getting enterprise grade stuff for their home lab make a mistake like that, I did some similar things, my biggest mistake was spending $300 on non-refundable ECC RDIMMs without realising that my server (the cheapest Dell Txxx server) took ECC UDIMMs.

I hope that my blog posts on these topics will save some people some money.

burnt-resistor• 2 days ago

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.

ECC and DDR5

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