Minimizing power dissipation during write operation to register files

This paper presents a power reduction mechanism for the write operation in register files (RegFiles), which adds a conditional charge-sharing structure to the pair of complementary bit-lines in each column of the RegFile. Because the read and write ports for the RegFile are separately implemented, it is possible to avoid pre-charging the bit-line pair for consecutive writes. More precisely, when writing same values to some cells in the same column of the RegFile, it is possible to eliminate energy consumption due to precharging of the bit-line pair. At the same time, when writing opposite values to some cells in the same column of the RegFile, it is possible to reduce energy consumed in charging the bit-line pair thanks to charge-sharing. Motivated by these observations, we modify the bit-line structure of the write ports in the RegFile such that i) we remove per-cycle bitline pre-charging and ii) we employ conditional data dependent charge-sharing. Experimental results on a set of SPEC2000INT / MediaBench benchmarks show an average of 61.5% energy savings with 5.1% area overhead and 16.2% increase in write access delay.