Fault tolerant computer memory systems and components employing dual

Abstract

In a memory system comprising a plurality of memory units each of which possesses unit-level error correction capabilities and each of which are tied to a system level error correction function, memory reliability is enhanced by providing means for disabling the unit-level error correction capability, for example, in response to the occurrence of an uncorrectable error in one of the memory units. This counter-intuitive approach which disables an error correction function nonetheless enhances overall memory system reliability since it enables the employment of the complement/recomplement algorithm which depends upon the presence of reproducible errors for proper operation. Thus, chip level error correction systems, which are increasingly desirable at high packaging densities, are employed in a way which does not interfere with system level error correction methods.