Developing a Multicore Platform Utilizing Open RISC-V Cores

RISC-V has been experiencing explosive growth since its first appearance in 2011. Dozens of free and open cores developed based on this instruction set architecture have been released, and RISC-V based devices optimized for specific applications such as the IoT and wearables, embedded systems, AI, and virtual, augmented reality are emerging. As the RISC-V cores are being used in various fields, the demand for multicore platforms composed of RISC-V cores is also rapidly increasing. Although there are various RISC-V cores developed for each specific application, and it seems possible to pick them up to create the most optimized multicore for the target application, unfortunately it is very difficult to realize this in reality. This is mainly because most open cores are released in the form of a single core without cache coherence logic, which requires expensive design effort and development costs to address it. To tackle this issue, this paper proposes a method to solve the cache coherence problem without additional effort from the developer and to maximize the performance of the multicore composed of the RISC-V core selected by the developer. Along with a description of the sophisticated operating mechanisms of the proposed method, this paper details the architecture and hardware implementation of the proposed method. Experiments conducted through the prototype development of a RISC-V multicore platform involving the proposed architecture and development of an application running on the platform demonstrate the effectiveness of the proposed method.