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DDR5 include on-die ECC. Which is very different from traditional ECC. But many vendors marketing (and many enthusiasts are talking) as if it's the same. See [0], there's some really good explanations in the replies.

[0] https://twitter.com/iancutress/status/1401834748402716672

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Well, does anyone have any stats for how often memory errors happen inside the module vs. in transit?

My impression has been that the vast majority are the former, and those are pretty well fixed by on-die ECC.

But I will say I'm annoyed that there's no way to get datapath ECC without buying 25% extra chips and dealing with worse prices and speeds. Why can't a tiny chip on the module calculate those 8 bits on the fly?

Fake parity ram was a thing back when parity ram was also a thing. Fake ECC ram could also become a thing. It's easy enough to calculate the values on the fly.

Interesting to look at, though it would have to get really popular again to be worth it. I'll keep my fingers crossed.

And to be clear I don't want fake parity. I want it to verify the internal parity and then use those bits to calculate the data bus parity. Instead of paying 25% extra to get two layers of parity.

12% extra to go from zero parity to full parity was a much better offer than 25% extra to go from mostly-parity to mostly-double parity.

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