Partitioned Hybrid Encoding to Minimize On-Chip Energy Dissipation ofWide Microprocessor Buses

Dynamic bus power dissipation, especially for long global signal buses, is becoming increasingly important with technology scaling due to several reasons: more pronounced interwire coupling effects, higher frequencies, greater traffic demands arising from higher levels of integration (e.g., as seen in system-on-chip and multi-core designs), and power density concerns, among others. While low-power dynamic bus encoding schemes, such as bus invert (BI) and odd-even bus invert (OEBI), have been proposed to reduce bus switching activities, they are not effective for wide microprocessor buses carrying correlated traffic found in typical workloads like SPEC CPU2000 benchmarks. To address this, we propose a partitioned hybrid bus encoding technique in which the bus is partitioned optimally and the most energy-efficient dynamic encoding scheme- we consider bus invert (BI), odd/even bus invert (OEBI), and not encoding as the possible options, but any other collection of schemes can be considered-is independently applied to each partition depending upon traffic value characteristics to minimize total bus (wire self and interwire coupling) dynamic energy. While BI and OEBI provide average energy reductions of only 5.27%/1.58% and 0.98%/1.97% for data/instruction buses, respectively, for SPEC CPU2k benchmarks, our hybrid encoding technique yields average energy savings of 22.07%/27.40% for the same traffic and buses-these results take into account the energy consumed by control lines, too