The communication latency problem is presented with special emphasis on RISC (reduced instruction set computer) based multiprocessors. An interprocessor communication model for parallel programs based on locality is presented. This model enables the programmer to manipulate locality at the language level and to take advantage of currently available system hardware to reduce latency. A hardware node architecture for a latency-tolerant RISC-based multiprocessor, called Seamless, that supports this model, is presented. The Seamless architecture includes the addition of a hardware locality manager to each processing element, as well as an integral runtime environment and compiler