Recovery/serviceability system test improvements for the IBM ES/9000 520 based models

To assist recovery and serviceability testing, the authors dramatically increased the amount of error injection hardware built into the logic of the ES/9000 520 based models. Compare circuits were incorporated into each functional element such that, under program control from either the processor controller or instructions executing on the processor, hardware malfunction conditions could be injected in any element. These hardware malfunctions could be synchronized to occur under a vast majority of the command and data transfer operations that occur during normal machine operation. Also, they combined recovery and serviceability system testing. In system testing, they verified recovery and serviceability with a single fault injection, halving the number of hardware fault injections required.<>