Continuous scaling of CMOS technology push circuit designs towards multi-core complex SoCs. Moreover, with the nanometric technologies, the integrated system performances after fabrication will not be fully predictable. Indeed, the process variations really become huge at the chip scale. Therefore the design of such complex SoCs in the nanoscale technologies is now constrained by many parameters such as the energy consumption and the robustness to process variability. This implies the need of efficient algorithms and built-in circuitry able to adapt the system behavior to the workload variations and, at the same time, to cope with the parameter variations which cannot be predicted or accurately modeled at design time. In this context, this thesis work addresses the design of GALS-based NoC architectures in the upcoming CMOS technologies. A novel methodology to dynamically control the speed of different voltage-frequency NoC islands according to the process variability impact on each domain is proposed. This control technique can improve the performances, the energy consumption, and the yield of future SoC architectures in a synergistic manner. The control methodology is based on the design of an asynchronous programmable self-timed ring where the controller takes into account the dynamic workload and the process variability effects. The controller especially considers the operating frequency limit which does not exceed the maximum locally allowed value for a given clock domain. With such an approach, it is no more required to separately guaranty the performance for each node. This drastically relaxes the fabrication constraints and helps the yield enhancement. |
