Amdahl Corporation

Silas P Elash

Gary S Goldman

Jeffrey L Baker

Recovery of data from a store-to cache in a malfunctioning CPU, is accomplished without exercising the hardware of the malfunctioning CPU. A data path which is independent of the normal operating paths of the computer, such as a scan facility, is used to move data out of the cache into the mainstore while the malfunctioning CPU's clocks are off. A system controller controls normal transfer of data between the cache memory of the processing unit and the mainstore. A service processor is coupled to the processing unit, the mainstore, and the system controller, and is responsive to the detection of errors in the processing unit, for stopping the processing unit and moving data out of the cache memory to the mainstore through the scan facility separate from the system controller. Logic in the system controller flushes the move out queue or other storage locations in the system controller. After the data in the system controller has been flushed, the service processor moves the data from the cache memory into the mainstore. This prevents data moved out of the cache in the mainstore from being overwritten by move outs which were pending in the system controller at the time that the CPU was stopped.

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San Jose, CA, United States of America

Silas P Elash