From an old article published by Puget Systems in 2013 [1]:
> Finally, ECC RAM is slightly slower than non-ECC RAM. Many memory manufacturers say that ECC RAM will be roughly 2% slower than standard RAM due to the additional time it takes for the system to check for any memory errors. To verify this, we examined multiple benchmarks that we run on each system we produce. By using comparable CPUs (For example: Intel Core i7 4771 3.5GHz Quad Core 8MB versus Intel Xeon E3-1275 V3 3.5GHZ Quad Core 8MB) we found that this 2% estimate to be roughly correct. Our own benchmarks showed a performance hit ranging from .72 to 2.2% which, given normal testing deviations, is right in line with the 2% estimate.
I wasn't commenting on the speed of ECC memory, although from what I've seen manufacturers don't offer ECC memory modules with a speed as high as non-ECC versions.
Anyway what bugs me about Zen < 4 is that you can install ECC memory, but you can't be sure that ECC is really working on some motherboards.
For Zen 4 at least there's DDR5 with its on-die ECC, but the path to the CPU might still be unprotected.
> manufacturers don't offer ECC memory modules with a speed as high as non-ECC versions.
Indeed, they seem to be aiming their ECC sticks at the server market, their "overclockable" sticks at the gamer market, and not mixing the two. Perhaps this would change if more workstation motherboards officially supported ECC.
In the meantime, I suspect today's ECC RAM and X3D cache CPUs might complement each other well.
> For Zen 4 at least there's DDR5 with its on-die ECC, but the path to the CPU might still be unprotected.
Some Zen 4 motherboards do support ECC. ASUS lists it in their manuals and exposes settings for it in their EFI setup, for example.
As for being sure that it's working, I suppose that depends on the OS. This addition in Linux 6.5 looks helpful:
You can most certainly test ECC functionality on unqualified boards using a Linux LiveCD/USB. And there are plenty of boards that have gone through the process of getting ECC qualified, and advertise the feature. ASUS, for instance.
Does something prevent Zen 5 CPUs from using ECC memory?
Or maybe you mean that ECC puts more load on the memory controller, potentially reducing top RAM speed compared to non-ECC configurations?