A memory system includes a memory module and a memory controller. The memory module includes data chips that store data and are assigned to a first sub-channel that generates a first code word or a second sub-channel that generates a second code word, where the first code word and the second code are used to fill a single cache line. The memory controller, upon detection of a hard-fail data chip among the data chips, copies data from the hard-fail data chip to the ECC chip, releases mapping between the hard-fail data chip and corresponding I/O, and defines new mapping between the ECC chip and the corresponding I/O pins.