Fuzzy Control for Enforcing Energy Efficiency in High-Performance 3D Systems

Abstract—3D stacked circuits reduce communication delay in multicore system-on-chips (SoCs) and enable heterogeneous integration of cores, memories, sensors, and RF devices. However, vertical integration of layers exacerbates the reliability and thermal problems, and cooling is a limiting factor in multi-tier systems. Liquid cooling is a highly efficient solution to overcome the accelerated thermal problems in 3D architectures; however, liquid cooling brings new challenges in modeling and runtime management. This paper proposes a novel controller for improving energy efficiency and reliability in 3D systems through liquid cooling management and dynamic voltage fre-quency scaling (DVFS). The proposed fuzzy controller adjusts the liquid flow rate at runtime to match the cooling demand for preventing energy wastage of over-cooling and for maintaining a stable thermal profile. The DVFS decisions provide chip-level energy savings and help balancing the temperature across the system. Experimental results on 8- and 16-core multicore SoCs show that the controller prevents the system to exceed the given threshold temperature while reducing cooling energy by up to 50 % and system-level energy by up to 21 % in comparison to using a static worst-case flow rate setting. I