Traditionally the problem with building “real” open hardware is that it is never really going to be open. While the RISC-V open-source architecture, created by researchers at Berkeley, has been around since 2010 no one had bothered to use it. So eventually, as you worked your way down and reached the silicon it meant that — at least until very recently — your silicon was going to be proprietary. Your hardware was not open.
Late last year, the Bay Area startup SiFive announced the Freedom Everywhere 310 — the first commercially-available open-source SoC based on the RISC-V architecture. The RTL — the register transfer level — for the cores are freely available on GitHub.
However if you wanted to integrate a RISC-V core into your own chip, things were still a bit problematic. This changed last week when SiFive announced that their Coreplex IP architecture was available for licensing. Their RISC-V core designs can be licensed for a fixed price because, unlike ARM, the company is not intending to charge a per-core licensing fee.
SiFive’s website has all the information a designer needs to study the IP, including full datasheets, specifications and app notes, all available without an NDA. With one click, the designer can get instant access to full FPGA bitstream models to test software, SDK and tools. Fully functional, synthesizable evaluation RTL is also available instantly, allowing the designer to synthesize and simulate in their own design environment and process nodes. Finally, a simple seven-page contract with transparent pricing makes it straightforward and easy to license the IP for commercial use.
The Coreplex architecture includes the E31 core—a 32-bit processor, intended to replace an ARM Cortex-M3 inside sensors and wearables—and the E51 core, a 64-bit processor designed to serve as a controller in larger chips.
If you want to pick up your own RISC-V based board and start playing around with it, the HiFive1—open source, and Arduino compatible—is available on Crowd Supply. The board is based around the SiFive FR310 SoC.