In this paper, we test a Design Structure Matrix (DSM) based method for visualizing and measuring software portfolio architectures. Our data is drawn from a power utility company, comprising 192 software applications with 614 dependencies between them. We show that the architecture of this system can be classified as a “core-periphery” system, meaning it contains a single large dominant cluster of interconnected components (the “Core”) representing 40% of the system. The system has a propagation cost of 44% and architecture flow through of 93%. This case and these findings add another piece of the puzzle suggesting that the method could be effective in uncovering the hidden structure in software portfolio architectures.