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Comment by derefr | Hacker News Reader

ECC RAM is a bit of a hard case in that the memory controller needs a slightly different wire protocol for ECC vs. non-ECC DIMMs. "Back in the old days", this was one of the justifications for having a northbridge separate from the CPU. Now, in the name of efficiency, it's all on-chip, making ECC a processor feature rather than a motherboard feature.

That being said, it'd certainly be possible to fix this: just ask RAM manufacturers to make their non-ECC memory have the same pin out as ECC memory, with the ECC pins just stubbed to always report that everything is okay. Then all processors could just include the ECC version of the memory controller.

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While not exactly what you were suggesting, DDR4 ECC DIMMs and SO-DIMMS are already "pin compatible" with non-ECC modules. So it is straightforward to design a CPU and motherboard that support both, with a control bit in the IMC allowing the BIOS to enable/disable ECC checking (and the extra ECC byte lanes) iff ECC modules are installed (and that's what AMD did with Ryzen).

It is fair to say that Intel blocks ECC on its desktop i7 parts for non-technical/business reasons (i.e. so they can sell a higher-profit E3 Xeon if you want DRAM data integrity beyond what non-ECC memory can provide).

Interestingly, this is not true for DDR3 ECC SO-DIMMs. BTW, even AMD Bristol Ridge supports ECC I believe.

All processors do included the ECC version of the memory controller. Perhaps you're thinking of registered memory, which isn't supported by consumer-grade processors or the workstation/low-end server processors that use the same sockets?

This is not accurate, all (modern) AMD processors can work with both ECC and non-ECC ram, and ECC and non-ECC can even fit into the same ram sockets (the keying is different however, but a board can be compatible with both)

> the keying is different

I don't think it is. DDR3 UDIMMs, EUDIMMs, RDIMMs and LRDIMMs all use the same physical format.

And yet the Pentium G4560 -- one of the cheaper models of their Kaby Lake lineup -- supports both ECC and non-ECC RAM. I suspect the only reason behind lack of ECC support on their mainstream processors is just market segmentation.

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