On-Chip ECC, it's an improvement but full ECC memory, which you can get for DDR5, also protects your data in transmission at 6400MT/s.
Additionally the on-chip EEC of DDR5 won't report the errors to your OS. ECC memory errors when corrected can be handled by the OS, and you'll even be informed of the uncorrectable 2 bit errors.
Want to protect for 2-bit errors? Make sure your platform has support for ECC-chipkill.
While technically true, that DDR5 comes with "on-die ECC", it is only because the memory is so unreliable it will not work properly without it.
However, even then, it is not the same as true ECC that have a extra data correction chip on the memory module and also protects against send errors to the CPU.
Additionally the on-chip EEC of DDR5 won't report the errors to your OS. ECC memory errors when corrected can be handled by the OS, and you'll even be informed of the uncorrectable 2 bit errors.
Want to protect for 2-bit errors? Make sure your platform has support for ECC-chipkill.