There are a lot of 386/486/Pentium-based personal computers (PCs) out there. They are affordable, reliable, and offer good performance. Thus, it is only natural to think of networking multiple PCs to create a high-performance parallel machine - the problem is that conventional networking systems cannot provide low latency synchronization and communication. Low latency allows fine grain parallelism; the longer the latency, the fewer the programs that can achieve good speedup through use of parallelism. Typical parallel machines constructed using PC networks (e.g., PVM software using Ethernet hardware) generally have latencies between 0.001s and 0.1s. Even the "best" commercially-available parallel computers can do no better than a latency corresponding to the time to execute hundreds to thousands of floating-point operations. In contrast, PAPERS (Purdue's Adapter for Parallel Execution and Rapid Synchronization) provides a latency corresponding to execution of just a few floating-point operations. Despite this, PAPERS can be implemented at a cost of less than $50/PC, including cables.
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