Novel Vth Hopping Techniques for Aggressive Runtime Leakage Control

The continuous increase of leakage power consumption in deep sub-micro technologies necessitates more aggressive leakage control. Runtime leakage control (RTLC) is effective, since runtime circuits generally have significant amount of idleness. However, current RTLC techniques are only used when circuits have long idleness, rendering the techniques less profitable. The reason is due to the large energy and delay overhead when performing RTLC mode transition. We propose two novel techniques, workload-adaptive Vth hopping (WAVTH) and hierarchical Vth hopping (HIVTH), to tackle the overhead problems and enable aggressive runtime leakage control. Experimental results show 19.2 % average improvement on leakage saving with WAVTH and HIVTH over basic Vth hopping. The optimum design points of these two techniques are determined through accurate modeling.