VALVE: variable length value encoder for off-chip data buses

We propose variable length value encoding (VALVE) technique to reduce the power consumption in the off-chip data buses. While past research has focused on encoding fixed length data values to reduce the transition activity in the data buses, our proposed scheme is capable of detecting and encoding variable length bit patterns in the data values. VALVE also does not require prior knowledge of input data and uses just one external control signal. We evaluate our proposed scheme using a large spectrum of benchmarks and we achieve an energy reduction of 58% on an average and up to 75% on some benchmarks. We also analyze the performance penalty incurred due to the codec delay, which is found to be 0.45% of the total program execution time. We find that VALVE requires a minimal area of 0.0486 mm², which can be easily implemented with in a memory controller.