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Comment by Aurornis | Hacker News Reader

It's a valid question if you're not familiar with the RAM market. Sorry you're getting downvoted for it.

The manufacturers make the individual chips, not the modules (DIMMs). (EDIT: Some companies that make chips may also have business units that sell DIMMS, to be pedantic.)

The R in RDIMM means register, aka buffer. It's a separate chip that buffers the signals between the memory chips and the controller.

Even ECC modules use regular memory chips, but with extra chips added for the ECC capacity.

It can be confusing. The key thing to remember is that the price is driven by the price of the chips. The companies that make DIMMs are buying chips in bulk and integrating them on to PCBs.

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> Even ECC modules use regular memory chips, but with extra chips added for the ECC capacity.

Quite a few unbuffered designs in the past had a "missing chip". If you ever wondered why a chip was missing on your stick, it's missing ECC. Don't know if it's still the case with DDR5 though.

I have not seen that yet DDR5, I think the signal integrity requirements are too high now to even have unused pads open. Most sticks don’t appear to have many traces at all on the top/bottom sides, just big power/ground planes.

Also with DDR5 each stick is actually 2 channels so you get 2 extra dies.

There's some new half assed ECC type of RAM, not sure the name.

Was reading a series of displeased posts about it. Can't seem to find it now.

On die ECC for DDR5. Which corrects locally but does not signal the host or deal with data between the die and the CPU.

Thanks, drove me bananas trying to find that again.

Presumably this is being marketed indistinguishably from regular ECC RAM?

If so, that's terrible news. It was already difficult enough to find ECC RAM for "workstation" class machines (i.e.: High end, non-server CPUs that support ECC such as AMD Threadripper).

It's not - ECC RAM still means real, between the RAM and CPU ECC. It's literally an extra 8 bits per channels, for an extra 16 bits per dim. 40 bits vs 32.

There's 9 bits in an ECC byte.

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