A Recovery Cache for the PDP-11

Backward error recovery is an integral part of the recovery block scheme that has been advanced as a method for providing tolerance against faults in software; the recovery cache has been proposed as a mechanism for providing this error recovery capability. This correspondence describes a recovery cache that has been built for the PDP-11 family of machines. This recovery cache has been designed to be an "add-on" unit which requires no hardware alterations to the host CPU but which intersects the bus between the CPU and the memory modules. Specially designed hardware enables concurrent operation of the recovery cache and the host system, and aims to minimize the overheads imposed on the host.