July London Open Source Meetup for RISC-V

London RISC-V Group
Mon, Jul 19, 6:00 PM (BST)

10 RSVP'ed

About this event

Our quarterly meetup for the London open source community, focusing on RISC-V and open source, hosted by the BCS Open Source Specialist Group and the UK Open Source Hardware User Group. These meetings provide an opportunity to share the latest ideas around open source in the RISC-V ecosystem, combined with plenty of time for networking. The theme for this quarter’s meeting is optimizing code size for RISC-V.

We’ll be live streaming using BigBlueButton to provide a rich online experience for participants. As always the talks will be recorded for later upload to YouTube. You are invited to join and socialize from 18:00, talks will run from 18:30-20:00 with 30 minutes at the end for further discussion and socializing.

There is no requirement to register, you can just connect to livestream using BigBlueButton on this link. We are also recording the talks for later posting on our YouTube channel.

The livestream link will be open from 18:00 for networking, and the event will start at 18:30 prompt. We’ll keep the link open afterwards for discussion.


CFU Playground: Model-specific Acceleration on FPGAs

Tim Callahan, Google

This talk describes the CFU Playground, an open-source framework that an engineer, intern, or student can use to design and evaluate enhancements to an FPGA-based soft RISC-V processor, specifically to increase the performance of machine learning (ML) tasks through the addition of custom function units (CFUs). The goal is to abstract away most infrastructure details so that the user can get up to speed quickly and focus solely on adding new processor functions, exploiting them in the computation, and measuring the results.

The presentation describes the process of identifying hot spots in the code during an inference using a specific model, constructing a CFU to support new custom instructions, modifying the TensorFlow Lite kernel library to use these new instructions, measuring the results, and iterating. The goal is not to design a general ML accelerator; the goal is to jointly specialize the processor and ML kernels just for the model of interest.

All IP and software used is open sourced and licensed permissively — the open RISC-V ISA that allows new custom instructions, the VexRiscv soft core implementation, the LiteX system-on-chip IP, the Symbiflow FPGA toolchain, Renode and Verilator simulators, and TensorFlow Lite kernel libraries. Thus, the combined CPU, CFU, and kernel libraries that the user develops are not tied to any particular FPGA vendor; there are no licensing restrictions or fees; and there is no dependence on any black box proprietary tools.

Pineapple One: an open-source discrete 32-bit RISC-V CPU

Filip Szkandera

This talk will be about a 32-bit homemade RISC-V CPU, made only out of discrete logic components and memories. There are no FPGAs nor any microcontrollers used and the whole project can be found on GitHub as open-source. The goal of this project is to introduce more people to RISC-V with a CPU that can be build by anybody who can solder. The presentation will be supplemented by a live demo of the CPU as well as some plans for the upcoming version.

Q&A with Olof Kindgren, creator of SERV

Olof Kindgren, FOSSi Foundation

The award-winning SERV is the world’s smallest RISC-V CPU. But how does it work, what makes it so small and what is it good for? This is your chance to participate in a fully immersive multimedia edutainment experience to learn all the answers.


  • Tim Callahan

    Tim Callahan


    See Bio
  • Filip Szkandera

    Filip Szkandera

    See Bio
  • Olof Kindgren

    Olof Kindgren

    See Bio

  • Host

  • Jeremy Bennett

    Jeremy Bennett



  • Organizer

  • Sarah Cook

    Sarah Cook



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