ECC and DDR5

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ECC and DDR5

zdw

Comments (126)

jcalvinowens
> One thing that concerns me is the possibility of on-die ECC interacting with ECC on the motherboard and reducing it’s effectivenessDDR5 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.
nu11ptr
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.
nahuel0x
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.
Havoc
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.
hangonhn
"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.
cyanmagenta
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.
sandreas
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
Does encrypted memory give ECC-like detection benefit, along with rowhammer protection, for cheaper cost (only additional computation), and 100% reliable?
howard941
ECC is essentially mandatory for ZFS. Assuming that is you prefer your data uncorrupted.
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.
snvzz
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.
exabrial
> 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.
monster_truck
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 offThe 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.
AlexandrB
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.
ck2
16GB ECC DDR5 was $50 early 2025it is now $500when the AI/datacenter bubble finally bursts we are going to have some amazing hardware deals
lightedman
"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?