Scan based guided probe technology delivers Cyclone to the market

The author discusses how Tandem Computers used scan-based guided probe technology, built on Tandem´s implementation of scan, to build a functional test station quickly in order to help deliver its latest fault-tolerant mainframe computer, Cyclone, to the market in a timely manner. During the engineering alpha phase, in-circuit test was not fully in place and SETS (Sophisticated Engineering Test Station) was used exclusively to functionally test and debug all boards. More than 90%, yield was achieved at the next stage of integration using pseudorandom scan test for screening and high-grade test, and the guided probe traceback and microdiagnostics for debugging. However, debugging time was anywhere from 30 min to 4 h. As the knowledge base increased and one progressed up the learning curve, debugging time on guided probe traceback averaged less than 20 min. It is claimed that more than 97% yield at the next stage can be achieved. The production technicians are happy with the flexibility of guided probe traceback and the simplicity of maintenance provided by WIZ3 and supporting software