Ecole Polytechnique Federale De Lausanne

Paolo Ienne

Laura Pozzi

Nikil Dutt

Miljan Vuletic

Partha Biswas

Reconfigurable Systems-an-Chip (RSoCs) on the market consist of full-fledged processors and large Field-Programmable Gate Arrays (FPGAs). The latter can be used to implement the system glue logic, various peripherals, and application-specific coprocessors. Using FPGAs for application-specific coprocessors has certain speedup potentials, but it is less present in practice because of the complexity of interfacing the software application with the coprocessor. In the present application, we present a virtualisation layer consisting of an operating system extension and a hardware component. It lowers the complexity of interfacing and increases portability potentials, while it also allows the coprocessor to access the user virtual memory through a virtual memory window. The burden of moving data between processor and coprocessor is shifted from the programmer to the operating system.

Virtual memory window with dynamic prefetching support

Instruction Set Extensions (ISEs) can be used effectively to accelerate the performance of embedded processors. The critical, and difficult task of ISE selection is often performed manually by designers. A few automatic methods for ISE generation have shown good capabilities, but are still limited in the handling of memory accesses, and so they fail to directly address the memory wall problem. We present here the first ISE identification technique that can automatically identify state-holding Application-specific Functional Units (AFUs) comprehensively, thus being able to eliminate a large portion of memory traffic from cache and main memory. Our cycle-accurate results obtained by the SimpleScalar simulator show that the identified AFUs with architecturally visible storage gain significantly more than previous techniques, and achieve an average speedup of 2.8&#xd7; over pure software execution. Moreover, the number of required memory-access instructions is reduced by two thirds on average, suggesting corresponding benefits on energy consumption.

Growing community of inventors

Pully, Switzerland

Paolo Ienne