Partial bus-invert coding for power optimization of application-specific systems

Reviewer: Farnaz Toussi

This paper extends the conventional bus-invert (BI) coding to reduce the number of bus transitions, and thus, the dynamic power consumption. The proposed coding, partial bus-invert (PBI), simply divides the bus into two or more subbuses, and based on the last transition pattern and the current transition pattern, determines whether or not to invert a subbus. In particular, if less than half of the bus lines within a subbus cause a transition, the subbus is inverted and the invert line of the subbus is set. The experimental results indicate significant reduction in bus switching. However, one of the limitations of this scheme is that the access patterns must be known ahead of time in order to divide the bus into subbuses and add additional invert lines (one per subbus). Although more subbuses show significant improvement, the additional invert lines, I/O pins and I/O drivers limit the number of subbuses that can be implemented. Nevertheless, in addition to reducing power, the proposed scheme can potentially reduce the impact of crosstalk noise. Overall, the paper’s presentation is good, but the experimental results and their comparisons with previous work are not described well. In particular, in each experiment, the PBI is compared with a different scheme and the authors do not explain why this is the case. Online Computing Reviews Service