 The combination of CRC-32 and the chosen scrambler polynomial were evaluated by exhaustively enumerating all 4-bit error patterns for all possible packet sizes with an optimized C program.The main contribution of 64b/66b is the observation that deterministic run length and transition density of 8b/10b are not always worth a 25% code overhead, and that solid robust systems could be designed using statistically bounded methods.At some point, practical risks, whether from MTBF of components such as power supplies or from phenomena such as cosmic rays or solar flares, dominate the reliability of both 8b/10b and 64b/66b systems.