Techniques for minimizing and balancing I/O during functional partitioning

Recent work has demonstrated numerous benefits of functionally partitioning a behavioral process into mutually exclusive subprocesses before synthesizing each process into a custom digital-hardware processor. A key problem during partitioning is minimizing the input/output (I/O) pins or wires between processors. The traditional structural partitioning approach is strongly restricted by such I/O. We previously showed that the new approach of functional partitioning eases this restriction. We now demonstrate a further relaxation of the I/O restriction by introducing the FunctionBus interprocessor bus and the port-calling functional transformation. The FunctionBus allows choice of any size for internal I/O by trading off I/O size for performance, while port calling allows distribution of external I/O almost arbitrarily among modules. We describe experiments showing large I/O reductions through these techniques, with only small performance penalties.