The authors present a system tool, called SuperTracer, that not only meets the requirements of many distinct aspects of large software system testing, debugging, and maintenance, but does so in a completely nonintrusive manner. SuperTracer is a single multilayer printed circuit pack for DMS SuperNode controlled by software written in the Protel language. The authors discuss all aspects of the tool, including the basic architecture, recursive mechanism to overcome the uncertainties due to pipelining, and prefetching, and the reasons for broad acceptance among the design, test, maintenance, and support user communities. In many cases the users found that a solution to their particular scenario was reached in a fraction of the time previously needed for the same problem. >