alt Hacker News> 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.