FAUST: Design and implementation of a pipelined RISC-V vector floating-point unit

Abstract

In this paper, we present Faust, a pipelined FPU for vector processing-capable RISC-V core developed within the European Processor Initiative (EPI) project. Faust is based on the open-source multi-format floating-point architecture FPnew that was extended and redesigned to support the RISC-V Vector extension specification (RVV) 1.0 and the most recent IEEE 754-2019 FP standard. Faust is extensively tested, mature and configurable, enabling ease of integration, as will be demonstrated in the paper. Faust can produce two binary32 operations or one binary64 operation per clock cycle. We have also developed FPU-V, an update of the SoftFloat-based reference model as a critical part of the UVM-based universal and extensible FPU verification environment. Faust was integrated and taped out as part of Vitruvius, a RISC-V Vector Processing unit of the EPAC1.0, the first EPI Accelerator Test Chip in GlobalFoundries 22FDX technology, and was shown fully operational at a target frequency of 1 GHz.