DDR5 on-die ECC detects and corrects one-bit errors. It cannot detect two-bit errors, so it will miscorrect some of them into three-bit errors. However, the on-

DDR5 on-die ECC detects and corrects one-bit errors. It cannot detect two-bit errors, so it will miscorrect some of them into three-bit errors. However, the on-die error correction scheme is specifically specially designed such that the resulting three-bit errors are mathematically guaranteed to be detected as uncorrectable two-bit errors by a standard full system-level ECC running on top of the on-die ECC.