Abstract: A technique for reducing the overhead of daisy chain test mode in divide-and-conquer testing using intermediate test modes that do not span all cores or all flip-flops in the core. The partial residual test mode spans across a subset of the cores and allows to bound the number of cores that a full residual test mode may span across. The interaction of the cores among one another at the top-level is analyzed and the minimum number of flip-flops in a core that must participate in a intermediate test mode is selected. Algorithms are devised to analyze the interactions among the cores and build data structures which are used for identifying intermediate test modes. Using a reconfigurable scan segment architecture, intermediate test modes are implemented that are designed to work with all known test compression solutions.