International Business Machines Corporation

David Patrick Hillerud

Scott Barnett Swaney

Mark S Farrell

Philip George Emma

Charles Franklin Webb

Ferenc Miklos Bozso

Algirdas J Gruodis

Yiu-Hing Chan

Robert F Hatch

An exemplary embodiment of the invention is a method for holding up recovery unit (R-unit) operands for a minimum number of cycles, until all prior updates have completed, by comparing addresses in at least one queue and interlocking valid R-unit register address matches. The method includes receiving a plurality of R-unit register addresses and storing these R-unit register addresses in at least one queue. This method includes a write queue, a read queue, and a pre-write queue. Further, this method requires accessing these queues and comparing the R-unit register addresses therein. After the addresses are compared, the method determines whether there is a valid match between the R-unit register addresses and if so, implementing one of more interlocks.

Write before read interlock for recovery unit operands

A method for making a processor system immune to circuit failure caused by external noise using mirrored processors, and a recovery unit integral with the method, are disclosed. Identical addresses and data information is generated in each of two processors. The data is then partitioned into registers and Error Correction Codes (ECC's) are generated for the data. The address, data, and ECC information for each processor is then interlaced in a data structure. The interlaced structures of each processor are then compared. If the comparison yields no errors, the data is checkpointed in the recovery unit; if an error is detected, a recovery sequence can be initiated after the check-stop operation, whereby the system is restored to the last error-free checkpointing operation.

Recovery unit for mirrored processors

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Poughkeepsie, NY, United States of America

David Patrick Hillerud