RISC-V proponents tackle software ecosystem

SAN JOSE, Calif. — Now that RISC-V has established a beachhead as a deeply embedded controller in SoCs, it’s time to start asking the next question: Can this open-source instruction-set architecture (ISA) make the next big leap into being an alternative to Arm and the x86 as a host processor?

Editor's Note: This is part of an Aspencore Special Project on RISC-V. Other articles explore development tools, software libraries and open-source issues.

The short answer is yes, but it could take several years and there are plenty of pitfalls along the way. Essentially, the freewheeling open-source community behind RISC-V will need to develop and adhere to a wide range of system-level standards.

So far, Nvidia and Western Digital plan to use RISC-V controllers in their SoCs, and Microsemi will use it in a new FPGA. Andes, Cortus, and startup SiFive sell IP cores, and a handful of startups plan to launch mainly machine-learning accelerators using it.

RISC-V is in as many as 20 million fitness bands and smartwatches in China. In the U.S., SiFive has shipped more than 2,500 development boards using processors that it aims to sell as IP cores or as SoCs through its design services.

“The lowest-hanging fruit is the embedded space where the APIs are not exposed to programmers,” said Rick O’Connor, executive director of the non-profit RISC-V Foundation. “That’s the easiest thing to do, but there’s healthy activity in all segments.

“There are implementations in every facet of processor architecture from mobile to machine learning, servers, automotive, deeply embedded real-time systems for factory automation, and everything in between,” he said.

text A SiFive development board linked to an FPGA board and SSD was used for a Fedora port. Click to enlarge. (Source: Richard W.M. Jones, Red Hat)

Although the ISA has been stable for months, it still lacks formal approvals. It’s core integer spec and at least some of a group of about a dozen other key specs will likely get ratified this year.

As soon as the specs are approved, the foundation aims to hammer out details of self-test compliance tests. Companies can run the tests to show that their products meet the specs.

As for software, a version of Fedora Linux is running on a SiFive Freedom Unleashed reference board, and several other Linux ports are in the works. A version of FreeBSD is available for RISC-V, and a Debian port is well underway. A Yocto embedded Linux port is in the works, as are versions of FreeRTOS and the open-source Zeyphr RTOS, said a RISC-V software expert at a talk in June.

The foundation just started work on a Linux boot spec, OpenSBI 0.1. Beyond Linux, there are no ports for Android, Windows, or other commercial OSes.

The bad news is that the OS ports are just the tip of a software iceberg.

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