FAULT DETECTION AND HANDLING ARRANGEMENTS FOR USE IN DATA PROCESSING SYSTEMS

A fault interrupt system is arranged, upon the detection of a fault to cause a processor in which the fault is detected to enter a fault check-out routine. Successive fault conditions detected while performing the fault check-out routine causes re-entry into that routine. A faulty processor is therefore, trapped within the fault check-out routine. Additionally the detection of a fault causes the master capability register of the fault detecting processor to be overwritten with a capability defining a special capability table which is only relevant to the fault check-out programs. By this mechanism the faulty processor cannot, even under fault conditions, gain access to any storage areas outside those of the fault check-out programs. In the multi-processor/multi-storage module system of the PP250 a number of copies of the fault check-out programs and related workspace areas on a one copy per store module basis are provided together with a special capability pointer for each processor of the system and each entry into the check-out program is performed using a different store and therefore entry mechanism into the check-out programs copy so that intermittent processor faults or particular storage module faults will not maintain the processor indefinitely in the check-out program.