Methods and apparatuses for synthesizing and/or implementing an augmented multimode compactor are described. An integrated circuit has circuitry that compacts test response data from scan chains in the integrated circuit under test. In many cases groups of the scan chains are coupled to output registers, such that a same group of scan chains is coupled to sequential elements of different output registers; and the same group is a subset of the scan chains including two or more scan chains. Various computer-implemented methods divide scan chains among at least groups and partitions. The groups disallow sharing a common scan chain from the scan chains, within a particular partition. At least one common scan chain is shared between the groups of different partitions.