Ncr Corporation

Wayne J Lewis

William P Ward

Allen G Taylor

Alan B Davison

Robert E Cichon

A memory system having a word-addressable memory and bit changing circuitry for changing or updating individual bits within the data words stored in the memory. The memory includes a primary memory and a copy memory. The copy memory stores duplicates of the data words stored in the primary memory. The bit changing circuitry receives a word having a bit to be changed from the copy memory and returns the word, including the changed bit, to both the primary memory and copy memory.

Memory system wherein individual bits may be updated

A processor having a pipeline architecture is comprised of a plurality of replaceable circuit units and includes a snapshot circuit associated with each replaceable circuit unit. Each snapshot circuit has a snapshot register for storing the signals at test points in its associated replaceable circuit unit in response to either an immediate snapshot command or a delayed snapshot command being executed by a processor. A command-under-test passing through the processor results in the signals at the test points. The delayed snapshot command delays the storing of the signals by the snapshot register so that by preceding the command-under-test by a delayed snapshot command, the signals at test points in the execute stage of the processor are stored during the execution of the command-under-test.

Method and apparatus for diagnosing faults in a processor having a

A data processing system implemented in LSI includes error detection and correction (EDC) circuits operating either in an error correction code (ECC) mode by generating ECC parity bits, or a byte parity mode by generating or checking byte parity bits. Each EDC circuit is identical and is capable of delivering identical control signals to byte sliced memory interface chips for purposes of error correction. The EDC circuits may be used individually with a 32 bit data bus or may be combined for use with a 64 bit data bus.

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Escondido, CA, United States of America

Wayne J Lewis