RISC-V SoftCPU Contest: Enter Now!


The RISC-V Foundation is proud to announce a RISC-V soft CPU core design contest sponsored by Google, Antmicro and Microsemi, a subsidiary of Microchip, Founding Platinum members of the RISC-V Foundation.

The aim of the contest is to further promote the use of the vendor-independent, modular and reusable ISA in FPGA applications, and push the limits of state-of-the-art by encouraging innovative FPGA soft CPU implementations of the RISC-V ISA.

The contest targets two FPGA platforms from RISC-V Foundation members Microsemi and Lattice Semiconductor. Participants have the option of using the larger 25K LUT Microsemi IGLOO™2 or SmartFusion™2, or the 5K LUT Lattice iCE40 UltraPlus™. The contest challenges contest participants to build either very small or high-performance soft RISC-V implementations, with additional points awarded for novel approaches to the implementation itself.


The entries will be RV32I-compliant soft CPUs. The core can support other standard extensions (e.g. ‘C’ or ‘M’) if the designers decide to do so.

Categories & Scoring

There are four categories the entries will compete in:

  • Smallest Microsemi SmartFusion®2 or IGLOO®2 implementation
  • Smallest Lattice iCE40 UltraPlus™ implementation
  • Highest-performance Microsemi SmartFusion®2 or IGLOO®2 implementation
  • Highest-performance Lattice iCE40 UltraPlus™ implementation

For the “smallest implementation” categories, the smallest number of total resources used is better. Total resources shall include Logic Elements, Math Blocks and internal RAM. In case of a draw, the entry with the higher performance is ranked higher.

For the “highest-performance implementation” categories, the performance of the entries will be measured using the Dhrystone benchmark compiled with the -O3 -fno-inline option.

50, 30 and 10 points will be awarded to any entry that ranks 1st, 2nd and 3rd in each category, respectively (so for example, if a given entry is the 2nd smallest on the Microsemi platform, it will be awarded 30 points). An entry targeting both the Microsemi and Lattice platforms can potentially be awarded points in categories for both vendors, if necessary files and instructions to reproduce are provided for both.

An additional pool of 100 points will be distributed between projects by a panel of five judges, selected from the members of the RISC-V Foundation, awarding up to 20 points each based on the creativeness of the entries submitted – participants are encouraged to try out novel approaches to creating their cores.

Minimum Requirements

The resulting design must be in Verilog (the core itself can be written in a framework such as Chisel, SpinalHDL or MiGen which generates Verilog) and be possible to be simulated using Verilator. The design must be a complete FPGA implementation targeting at least one of the two platforms and run the provided Zephyr RTOS application. The Zephyr 1.13 release should be used and can only be modified in a way that does not touch the OS core. Any modifications to the standard RISC-V GCC provided by Zephyr are strictly forbidden.

The CPU must pass the RISC-V RV32I compliance tests.

Also, the CPU must boot the following Zephyr applications:

Entries have to be submitted in the form of repositories on github.com with a clearly stated BSD-style license (the Apache 2.0 license is preferred) including:

  • the Soft CPU’s HDL code
  • constraint and other FPGA-related files necessary to produce a binary bitstream for the respective hardware
  • a README with a complete list instructions and prerequisites, as well as Makefiles or other scripts, needed to produce the bitstream. The README should also include instructions how to simulate the design in Verilator.
  • a binary version of the bitstream which can be fully and identically reproduced using the files and instructions mentioned above
  • any necessary Zephyr 1.13 files in the zephyr/ subdirectory (can be a git submodule)


Image result for microsemi logo

Microsemi IGLOO2 M2GL025/SmartFusion2 M2S025

25K 4-input LUTs

SmartFusion2 boards can be purchased from Future Electronics for $99.95.

Both boards feature the same 25K LUT FPGA fabric. SmartFusion2 is essentially identical to Igloo2 except that it is a SoC FPGA with a built-in Cortex-M3 hard CPU – the soft CPU to be designed should not use the hard CPU subsystems as such but interesting ways to enhance the design using the built-in hard CPU can be implemented.




Lattice iCE40 Ultra Plus – iCE40UP5K

5K 4-input LUTs

There are several boards with this part that can be used for the development:


1st prize: USD $6,000
2nd prize: USD $3,000 + Splash Kit + iCE40 UltraPlus MDP
3rd prize: USD $1,000 + PolarFire Evaluation Kit + iCE40 UltraPlus Breakout Board


Entries with links to the relevant GitHub repositories will be accepted at softcpu-contest@riscv.org by Nov. 26, 2018 at 11:59 p.m. PST.

Results will be announced at the 1st RISC-V Summit taking place in Santa Clara, Calif. from Dec. 3-6. Participants are not required to attend the RISC-V Summit to win. You can check out the agenda for the RISC-V Summit here and register here.