Error recovery in a central processing unit of vlsi, which is an address - and execution pipeline module is used

摘要

An error handling facility is disclosed which includes a central processing unit (CPU) incorporating a basic processing unit (BPU) including a pipelined AX unit (as well as a decimal numeric - DN - unit and a floating point - FP - unit) having a plurality of software visible registers and which issues an AX ERROR signal in response, among others, to sensed errors occurring within the AX unit during the processing and execution of instructions. An auxiliary (XRAM) memory receives, via a cache unit, and temporarily stores a record of the contents of the software visible registers concurrently with the availability of the result of each instruction executed by the AX unit. A clock unit is coupled to receive the AX ERROR signal and responds by suspending clock signals to the BPU as well as notifying a service processor (SP) of the error occurrence. The relevant contents of the XRAM are also forwarded to the SP for analysis, and the SP can order a restart by issuing a "resume" signal to the clock unit after the information obtained from the XRAM has been analyzed and the failing CPU reinitialised as necessary. The issuance of an AX ERROR occurring in the pipeline activity signal is delayed until all instructions in the pipe ahead of the faulting instruction have completed execution. Alternatively, the delay can be extended until all instructions in the pipe ahead of and including the faulting instruction have completed execution. IMAGE