While SiFive is most known for their RISC-V architecture designs, SiFive's OpenFive isn't limiting their custom silicon development to RISC-V but also supports Arm and other CPU ISAs for embracing heterogeneous mixed-ISA designs.
OpenFive is being promoted as ISA-neutral and RISC-V agnostic and will work with customers for AI, edge computing, HPC, and other workloads.
More details on SiFive's custom silicon offerings via OpenFive.com .