Scalable management of distributed resources is one of the major challenges in deployment of large-scale clusters. Management includes transparent fault tolerance, efficient allocation of resources, and support for all the needs of parallel computing: parallel I/O, deterministic behavior, and responsiveness. Meeting these requirements with commodity hardware and operating systems is difficult because they were not designed to support global management of a largescale system. In this paper we propose a small set of hardware mechanisms in the cluster interconnect to facilitate the implementation of a simple yet powerful global operating system. This system, inspired by concepts from the BSP and SIMD computational models, allows commodity clusters to grow to thousands of nodes while still retaining the usability and responsiveness of the single-node workstation. Our results on a software prototype show that it is possible to implement efficient and scalable system software using the proposed set of mechanisms.