Thanks, Hugh. I have spent many hours trying to make sense of this and come up to speed. Thanks for the links, and I'll definitely follow up with what I conclude. On Fri, 8 Nov 2024 at 00:31, D. Hugh Redelmeier via talk <talk@gtalug.org> wrote:
From: David Mason via talk <talk@gtalug.org>
I'm interested in this topic but have no time to research it. And the information is kind of hard to find. But google is powerful. So I spent an hour or two.
Please tell us what you find and conclude.
As I understand it, all DR5 does single-bit error correction, but it is up to the board/CPU to trap on multi-bit errors. I don't know if DDR5 writes bback the corrected bit, or if that's up to the other components.
I did not know that. I've now seen it stated elsewhere.
I do know that single-bit correction, with no reporting for correction and no reporting for detected multi-bit errors is not of any use to the user.
When I first saw a machine with ECC RAM (an IBM 370/145), the purpose of ECC was to allow the use of unreliable RAM chips. It did not actually help the user (except in price). I was so disappointed.
At one point I believed that IBM's phrase "chip kill" was relevant. ECC normally detects single-bit errors in a word but in many configurations, one dead chip will take out more than one bit in a word.
I don't know about the newest RAM technology.
Typically, memory modules for ECC were 72-bits wide: 64 bits of data and 8 check bits. That allows Hamming code to be used. Originally that extra 8 bits was meant to be used as a parity bit for each byte. It just happened to allow ECC, as long as the RAM was treated as 8-byte words.
(My Sun3/60 used parity on such RAM.)
I think that (some?) ordinary Ryzen's support ECC but that not many firmwares do. And perhaps not many chipsets do. Here's a kind of old link to Asus: <https://www.asus.com/support/faq/1045186/>
That was quite helpful. This seems to be closer to what I'm looking for:
https://www.newegg.ca/asrock-rack-x570d4u-supports-3rd-gen-amd-ryzen-process...
Maybe I'm too penny-wise but that seems pretty expensive.
There are hidden gems to be found.
- My ThinkServer TS-100 has a Haswell i3 and (surprise!) supports ECC. That's only partly a function of the chipset. i5 or i7 chips would not support ECC. VERY ODD. Note: this box cost me about $400 new, a decade ago, so ECC does not need to be expensive.
- < https://forums.servethehome.com/index.php?threads/lenovo-thinkcentre-thinkst...
notes that Lenovo ThinkCentre "tiny" computers with certain AMD processors and chipsets support ECC.
- I asked Bee-Link if my SER7 mini-PC with AMD Ryzen 7 7840HS supported ECC; they said no. That's not surprising since AMD says that it doesn't. Perhaps that is true of all laptop processors. < https://www.amd.com/en/products/processors/laptop/ryzen/7000-series/amd-ryze...
Unresearched threads:
Many Xeon chips support ECC. Some of those may be among the less expensive ones (i.e. aimed at workstations rather than servers).
(Almost) no Intel Core processors support ECC. I infer that this is a matter of market segmentation.
Lots of AMD processors support ECC but not all. The chipset and the firmware can veto this capability. I infer that the desktop processors with decent iGPUs ("G" suffix) don't support ECC. Note: recent desktop processors without G suffix have GPUs that are low performance but work -- perfect for servers where you might want a head.
Why the divergence? Market segmentation is best for a manufacturer of an expensive thing that competes with its own cheaper thing. Since AMD's main competitor as Intel, not itself, they threw in anything useful that didn't cost much to add.
Here's a random servethehome review that might be interesting. < https://www.servethehome.com/amd-ryzen-server-the-asrock-rack-1u4lw-b650-2l2...
Do look for more.
This thread has interesting and sometimes conflicting claims: < https://forum.level1techs.com/t/fun-intel-anecdote-qs-amd-ecc-mobos/216354/1...
This statement looked intriguing (talk about moving the goal posts!) DDR5 RDIMMs can and often do support 80-bit wide ECC (EC8). --- Post to this mailing list talk@gtalug.org Unsubscribe from this mailing list https://gtalug.org/mailman/listinfo/talk