Recent advances have blurred the lines a bit. The ECC memory that we all know and love is mainly side-band EEC, with the memory bus widened to accommodate the ECC bits driven by the memory controller. However as process size shrink, bit flips become more likely to the point that now many types of memory have on-die EEC, where the error correction is handled internally on the DRAM modules themselves. This is present on some DDR4 and DDR5 modules, but information on this is kept internal by the DRAM makers and not usually public.

https://semiengineering.com/what-designers-need-to-know-abou...

There has been a lot of debate regarding this that was summarised in this post -

https://blog.codinghorror.com/to-ecc-or-not-to-ecc/