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Current microprocessors employ a global timing reference to synchronize data transfer. A synchronous system must know the maximum time needed to compute a function, but a circuit usually finishes computation earlier than the worst-case delay. The system nevertheless waits for the maximum time bound to guarantee a correct result. As a first step in achieving variable pipeline delays based on data values, approximation circuits can increase clock frequency by reducing the number of cycles a function requires. Instead of implementing the complete logic function, a simplified circuit mimics it using rough calculations to predict results. The results are correct most of the time, and simulations show improvements in overall performance in spite of the overhead needed to recover from mistakes.