High-speed on-chip ECC for synergistic fault-tolerance memory chips

The placement of error-correcting-code (ECC) systems on dynamic-RAM (DRAM) chips poses many practical problems, among which are increased access time and chip size. The authors describe an optimized, self-contained, and self-timed on-chip ECC system embedded in a high-speed 16-Mb DRAM chip. This chip also has redundant word and bit lines. The combination of redundancy and on-chip ECC produces a synergistic effect which results in a major increase in fault tolerance for the hard manufacturing defects. It also improves the reliability of the chip, regardless of manufacturing defects. This improvement is attained with only a 5-ns penalty in access time and an 11% increase in chip size