Towards a Modular RISC-V based Many-Core Architecture for FPGA Accelerators

Multi-/Many-core architectures are emerging as scalable, high-performance and energy-efficient computing platforms suitable for a variety of application domains from edge to cloud computing. Recently, the appearance of RISC-V open-source ISA creates new possibilities to develop customized computing platforms with high savings in the non-recurring engineering costs. Moreover, the current trends toward open-source hardware frameworks are aimed to reduce design time and cost for complex system-on-chip architectures. Therefore, modularity and re-usability of hardware components are major challenges for flexible hardware architectures. The motivation behind this work is to introduce a modular cluster-based many-core architecture for FPGA accelerators that is re-usable and flexible tailored to implement different many-core taxonomies with less design time and costs by using regular and replicated sets of computing, memory, and interconnection blocks. The proposed many-core architecture is built using multiple processing clusters coupled with a NoC for communication which allows a high degree of design scalability. The processing cluster inside features a configurable multi-core architecture consisting of multiple RISC-V processing elements (PE) tightly coupled with a bus-based interconnection for intra-cluster communication using parameterized scratchpad shared memory. Each PE features a single RISC-V core with a tightly coupled parameterized scratchpad local memory and generic AXI interface. Evaluation results demonstrate that the proposed architecture features a scalable computing performance of 501 MOp/s for 4 clusters and 878 MOp/s for 8 clusters. Moreover, a scalable memory bandwidth up to 4.3 GB/s is achieved for 9 clusters with a power consumption of 1.4 W per cluster utilizing 7.7% of on-chip memory resources. The many-core architecture is implemented and evaluated on Xilinx Virtex Ultrascale+ with the feature of changing the architecture configurations during run-time using dynamic and partial reconfiguration which provides more flexibility and re-usability.