become popular for various reasons. Although originally aimed at reducing production test costs, they have quickly migrated to other niches and have proven useful in reducing not only cost, but time-to-market. Tracking the "use" spaces has resulted in identifying three clearly different areas of application: design-desktop, correlationlab, and the production-test floor. These spaces have defined tasks such as characterization, first silicon bringup, test program development, yield-learning diagnosis, and production probe, some of which will be described as case studies.