Our microcontroller-class RISC-V processor core Ibex for sure is a solid base with which to start your own project. Over the past months, we have invested a lot of effort in making the design more mature. This includes refactoring the RTL to make the design more understandable and programmer friendly, adding UVM-based verification to the source tree, but also integrating support for the RISC-V compliance suite and enabling publicly visible, open-source powered continuous integration (CI) to keep the design stable.
The lowRISC blog
Ibex, our small RISC-V core, is constantly changing. Roughly 50 percent of the RTL was refactored recently! We added features, tests, and cleaned the code up. We and our collaborators were able to make these changes (mostly) without breaking Ibex because we invested in testing: earlier this year we added UVM-based verification to the tree, and we run these tests after every change. We run static code analysis to catch common programming bugs.
In the past months, we have invested considerable effort in improving our RISC-V core Ibex. This 2-stage, in-order, 32-bit microcontroller-class CPU core was contributed to us by ETH Zürich in December 2018, with activity really ramping up since May. Having been taped out multiple times (as zero-riscy) in a mix of academic and industry projects, it came to us as a relatively mature code base. Despite this, we have continued to invest in improving its design and maintainability.
A few years ago lowRISC started developing a new LLVM backend targeting RISC-V. Rather than copying and modifying an existing backend, in an ad hoc fashion, we started from scratch and proceeded systematically. This approach proved successful in producing a high-quality codebase. We recently announced on the llvm-dev mailing list that the backend is now reaching stability and could be promoted from its current status of experimental to an official target.
On Monday I proposed promoting the upstream RISC-V LLVM backend from “experimental” to “official” for the LLVM 9.0 release. Responses so far are extremely positive, and we’re working to ensure this is a smooth process. This means that from 9.0, the RISC-V backend will be built by default for LLVM, making it usable out of the box for standard LLVM/Clang builds. As well as being more convenient for end users, this also makes it significantly easier for e.
On June 1st, Sam Elliott followed Laura and Pirmin in becoming lowRISC’s newest employee. A few weeks into his new role, he shares why he joined lowRISC and what he’s been doing since he started. “I joined lowRISC CIC as a Compiler Developer, working on the RISC-V LLVM backend, and so far I’m enjoying working on the team! Prior to lowRISC, I worked as a compilers and programming languages researcher at the University of Washington, where I completed my Masters degree.
Pretty much the whole team is in Zurich this week for the RISC-V Workshop and inaugural Week of Open Source Hardware, with a packed programme that got off to a start today and which runs all the way through to Friday afternoon. This morning lowRISC board member, Professor Luca Benini, gave a RISC-V Workshop keynote entitled, Energy efficient computing from Exascale to MicroWatts: The RISC-V playground. Our friends and close collaborators at PULP Platform are giving a number of talks this week and, we’re pleased to say, so are members of the lowRISC team!
At the beginning of many chips projects, there’s a dream. Could we create a more future-proof chip by embedding an FPGA fabric into it? Could we measure glucose levels more accurately by integrating a small bio lab onto a chip? Could we more reliably recognize kittens in a set of pictures by implementing neural network inference in hardware? In implementation, this dream becomes a piece of hardware, with digital or analog logic, sensors, actuators, and much more.
Pirmin Vogel and Laura James both joined lowRISC on May 1st this year. A few weeks in to their new roles, they each share thoughts on what attracted them to work at lowRISC. Pirmin: “After having traveled around the world for 6 months, I finally started my new position as hardware/software engineer at lowRISC C.I.C. in Cambridge at the beginning of May. At lowRISC, we are working on open-source hardware/software ecosystems with a fully open-sourced, Linux-capable, RISC-V-based SoC being the ultimate goal.
If you haven’t checked it out yet, be sure to take a look at our press release and the corresponding Google blog post. This industry support and growth of our board is a huge step forwards for lowRISC. As Royal Hansen, vice president of Security, Google, said: "Google believes that open source is good for everyone. To further our commitment, we are investing both capital and engineering resources to create a sustainable open source hardware ecosystem.