Arrangement for on-line diagnostic testing of an off- line standby processor in a duplicated processor configuration

Abstract From the Canadian patent

Under normal operating conditions in an on-line active/off-line standby duplicated processor system only the, on-line active processor is permitted access to the system's bus structure. The off-line standby processor is disconnected from the system buses. A technique is shown that allows the off-line standby processor diagnostic access to the system peripherals via the bus structure. The standby processor may then perform diagnostic testing to determine its communication ability with the system's peripheral devices. This diagnostic testing is done rapidly to avoid any loss of processor throughput. This technique also assures that the diagnostic testing will not cause faults or alter the …