All-Digital Energy-Constrained Controller for General-Purpose Accelerators and CPUs
Davide Zoni, Luca Cremona, William Fornaciari · IEEE Embedded Systems Letters · 2019
Considering the energy-cap problem in battery-powered devices, dynamic voltage and frequency scaling, and power gating represent the de-facto state-of-the-art actuators. However, the limited margin available to reduce the operating voltage, the impossibility to massively integrate such actuators on-chip together with their actuation latency force a revision of such design methodologies. We present an all-digital architecture and a design methodology that can effectively manage the energy-cap problem for CPUs and accelerators. Two quality metrics are put forward to capture the performance loss and the energy budget violations. We employed a vector processor supporting four hardware threads as representative usecase. Results show an average performance loss and energy cap violations limited to 2.9% and 3.8%, respectively. Compared with solutions employing the dynamic frequency scaling actuator, our all-digital architecture improves the energy-cap violations by 3× while maintaining a similar performance loss.