Rate-based vs delay-based control for DVFS in NoC

Minimization of power via DVFS in an NoC is possible, but may result in an intolerable increase of network delay. We examined two DVFS policies, a rate-based policy that scales down frequency and voltage to the minimum value that allows to sustain the injection rate without reaching saturation, and a delay-based policy in which a closed-loop control tunes frequency and voltage such that the NoC average delay tracks a target value. We evaluated the power-delay trade-off by means of network simulations and accurate power estimations after synthesis on a 28-nm FDSOI CMOS technology. Our results over synthetic and multimedia traffic patterns show that the first policy largely pays the better saving in power (20%-50% less than the second policy) with a large network delay increase (up to 3×). We then conclude that the delay-based policy offers a better power-delay trade-off.