Design of Thermal Management Control Policies for Multiprocessors Systems on Chip

The contribution of this thesis is a thorough study of thermal aware policy design for MPSoCs. The study includes the modelling of their thermal behavior as well as the improvement and the definition of new thermal management and balancing policies. The work is structured on three main specific disciplines. The areas of contributions are: modeling, algorithms and system design. This thesis extends the field of modeling by proposing new techniques to represent the thermal behavior of MPSoCs using a mathematical formalization. Heat transfer and modelling of physical properties of MPSoCs have been extensively studied. Special emphasis is given to the way the system cools down (i.e. micro-cooling, natural heat dissipation etc.) and the heat propagates inside the MPSoC. The second contribution of this work is related to policies, which manage MPSoC working frequencies and micro-cooling pumps to satisfy user requirements in the most effective possible way, while consuming the lowest possible amount of resources. Several families of thermal policies algorithms have been studied and analyzed in this work for both 2D and 3D MPSoCs including liquid cooling technologies. The discipline of system design has also been extended during the development of this thesis. Thermal management policies have been implemented in real emulation platforms and contributions in this area are related to the design and implementation of proposed innovations in real MPSoC platforms

Accurate Thermal Analysis Considering Nonlinear Thermal Conductivity

The increase in packing density has led to a higher power density in the chip which in turn has led to an increase in temperature on the chip. Temperature affects reliability, performance and power directly, motivating the need to accurately simulate the thermal profile of a chip. In literature, thermal conductivity is assumed to be a constant in order to obtain a linear system of equations which can be solved efficiently. But thermal conductivity is a nonlinear function of temperature and for silicon it varies by 22 % over the range 27 − 80 ◦ C[1]. If the nonlinearity of the thermal conductivity is ignored the thermal profile might be off by 10 ◦ C. Thus to get an accurate thermal profile it is important to consider the nonlinear dependence of the thermal conductivity on temperature. In this paper the nonlinear system arising out of considering the nonlinear thermal conductivity is solved efficiently using a variant of Newton-Raphson. In this paper we also study the abstraction levels under which the approximation of a periodic source by a DC source is valid. 1