[lazide]

Those only help isolate somewhat predictable errors. Which is rare for what ECC is designed to protect against.

If it’s a random, once in several billion reads/writes issue, it can just stop/identify the bad data from further propagating. Sometimes. That data is still lost.

ECC does forward error correction, which is extremely rare for the type of data protection you’re talking about. and if the data is corrupted in RAM (say when initially loaded/read) before the software can apply FEC, there is nothing the software can do.