Normally, the data path width for DIMMs is 64 bits but for the DIMMs that support ECC, the data path is 72 bits.
To add, error checking uses the extra 8 bits. ECC memory is more reliable than non-ECC memory but it costs more than a non-ECC memory. Comprising the DIMMS are a series of dynamic random-access memory integrated circuits. Mounted on a printed circuit board, these modules are designed for use in personal computers, workstations and servers.
The most common kinds of internal data corruption are detected and corrected by a type of computer data storage called error-correcting code memory.