Low power wide gates for modern power efficient processors

• A low power register file and tag comparator is proposed for modern superscalar microprocessors.
• The utilized technique is based on comparison of mirrored current of the evaluation network with its worst case leakage current.
• A 64×32, 2-read, 1-write ported register file and a 40-bit tag comparator are designed.
• Register file employed the proposed circuits CKCCD and CCD and a tag comparator is implemented using the proposed circuit CDL.
• The proposed designs are useful to designing low power processors with multi-ported register files and wide tag comparators.

In this paper, a low power register file and tag comparator is proposed which has lower leakage and higher noise immunity without dramatic speed degradation due to the wide fan-in gates. Simulation of register files and tag comparators designed is done using low-Vth 90 nm CMOS process technology model in all process corners. The results demonstrate 20% power reduction and 2× noise-immunity improvement in the implemented register file using the proposed circuit at the same delay compared to the standard domino circuits. On the other hand, simulation of tag comparators implemented using the other proposed circuit shows 41%, 22% and 7.5% reduction in power, delay and area, respectively compared to the standard footless domino at the same robustness condition. Moreover, the register file and the tag comparator designed with the proposed circuits respectively show 2.48 and 3 times improvement in the defined figure of merit compared to the counterpart circuits designed with the conventional domino circuit. Thus, the proposed are power efficient and suitable approaches for embedded processors with multi-ported register file and fully-associative caches with large number of tag comparators.