In this paper, we describe additions and modifications to the Computational Plant (Cplant/sup /spl trade//) system software to support multi-processor compute nodes and to support heterogeneous node types. We describe how these capabilities have been incorporated into our scalable runtime system and how these changes affect the interface seen by end users and application developers. We also discuss several important operating system and networking issues that can directly impact application performance. We present some initial performance metrics that indicate how our current implementation scales when multiple processes are running on a single node.