Application of scan hardware and software for debug and diagnostics in a workstation environment

An architecture for implementing scan technology for test and debug in a state-of-the-art workstation is described. Architectural features include controlling the scan and clock functions from a single resource that can also perform LFSR (linear feedback shift register) based pseudorandom testing and test result compression via signature capture. Operations of the scan subsystem are controlled from a service processor that uses a diagnostics bus to communicate with individual scan and clock resource units present on each system board. For debug purposes the service processor has been linked with a remote computer, and software has been developed to display and/or modify system state variables (flip-flops). Analysis of scan overhead indicates that benefits in test and debug of the target system far outweight the cost of implementing scan technology for the APOLLO DN10000 workstation