The evolution of sub-micron technologies has induced tremendous challenges the designer has to face, namely, the Process-Voltage-Temperature varibility and the decrase of power consumption for mobile applications.
The work to be done here concerns the DVFS (Dynamic Voltage and Frequency Scaling) policies for GALS (Globally Asynchronous, Locally Synchronous) architecture.
A fine grain modelling of the voltage and frequency “actuators” must be first done in order to simulate in a realistic ways the physical phenomena. Especially, the various parameters that may influence the system will be considered (process variation, supply voltage variation and noise, temperature variation, etc.)
Then, Non-Linear (NL) control laws that take into account the saturation of the actuators will be developed. These laws will be validated on the physical simulator and their performances in regulation (i.e. the response of the closed-loop system to disturbances such as PVT variations) will be evaluated. Note that these laws will be designed at the light of implementation constraints (mainly cost) in terms of complexity, area, etc.
Actually, the system considered here is intrinsically a Multi-Inputs-Multi-Outputs (MIMO) one. Therefore, its control can be design with NL techniques devoted to MIMO systems in order to ensure the requirements and reject the disturbances.
The control of several Voltage and Frequency Islands (VFI) is usually done via a “central brain” that chooses the voltage and frequency references thanks to a computational workload deadline. For more advanced architectures, the capabilities of each processing element, especially its maximum frequency, can be taken into account. A disruptive approach should be to consider a more distributed control that for instance takes into account the particular state (e.g. temperature) of each VFI neighbours. Control techniques that have been designed for distributed Network Controlled Systems could be adapted to MPSoCs.