What I’ve read is that DDR5 has “on-die ECC” which means that the module itself handles the error correction, but then it can not handle errors that happen in transit to the CPU as full ECC can.
There are DDR5 full-ECC modules that would be real equivalents to DDR4 ECC.
> When the latest version of DDR memory – DDR5 – was introduced in 2020, marketing campaigns got one important fact wrong. DDR5 UDIMM, the regular desktop RAM we’re all familiar with, was touted as having “built-in” Error Correcting Code (ECC). Not true. What it has is built-in data checking, which is a very different feature that shouldn’t be confused with traditional ECC. For that, your customers will need DDR5 ECC UDIMM memory.
— Intel, “Error Correcting Code (ECC) vs. Built-in Data Checking”: https://www.intel.com/content/www/us/en/content-details/7549...