Ambient variation-tolerant and inter components aware thermal management for mobile system on chips

In this work we measure and study two key aspects of the thermal behavior of smartphones: 1) thermal interaction between the components on the printed circuit board and 2) the influence of phone´s ambient temperature which is subject to large variations. The measurements on the smartphone running typical workloads show that the heat generated by the communication subsystem and the high temperatures on the back cover of the phone can increase the SoC temperature by as much as 17°C. None of the run-time thermal management studies presented to date considered this interaction, as there was no model available. We design a thermal model that captures this thermal dependency and a policy able to avoid thermal emergencies while minimizing the impact on performance.