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A Linux-capable host multicore for and by the world

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BlackParrot Logo

BlackParrot: A Linux-Capable Accelerator Host Multicore License Gitlab CI Contributers Twitter Follow

BlackParrot aims to be the default open-source, Linux-capable, cache-coherent, RV64GC multicore used by the world. Although originally developed by the University of Washington and Boston University, BlackParrot strives to be community-driven and infrastructure agnostic, a core which is Pareto optimal in terms of power, performance, area and complexity. In order to ensure BlackParrot is easy to use, integrate, modify and trust, development is guided by three core principles: Be Tiny, Be Modular, and Be Friendly. Development efforts have prioritized ease of use and silicon validation as first order design metrics, so that users can quickly get started and trust that their results will be representative of state-of-the-art ASIC designs. BlackParrot is ideal as the basis for a lightweight accelerator host, a standalone Linux core, or as a hardware research platform.

The BlackParrot Manifesto

  • Be TINY
    • When deliberating between two options, consider the one with least hardware cost/complexity.
  • Be Modular
    • Prevent tight coupling between modules by designing latency insenstive interfaces.
  • Be Friendly
    • Combat NIH, welcome external contributions and strive for infrastructure agnosticism.

Project Status

BlackParrot v 1.0 was released in March 2020 and has been up and running in the lab since April 2020. It supports configurations scaling up to a 16-core cache coherent multicore, including the baseline user and privilege mode functionality to run Linux. An optimized single core variant of BlackParrot (also Linux-capable) is also available. Currently, the core supports RV64IMAFD, with C support on the way!

Development of BlackParrot continues, and we are very excited about what we are releasing next!

A 12nm BlackParrot multicore chip was taped out in July 2019.


We presented BlackParrot at the ICS 2020 Workshop on RISC-V and OpenPOWER! slides

We first announced BlackParrot at FOSDEM 2020! slides video pdf

Getting Started

Tire Kick

Users who just want to test their setup and run a minimal BlackParrot test should run the following:

# Clone the latest repo
git clone
cd black-parrot

Install a minimal set of tools and libraries

For faster builds, make prep_lite -j is parallelizable!

make prep_lite

Running your first test

make -C bp_top/syn tire_kick

This should output (roughly)

Hello world!
    clk   :                  220
    instr :                   66
    mIPC  :                  300
All cores finished! Terminating...

Docker build

For a painless Ubuntu build, download and install Docker Desktop then run the following:

git clone
cd black-parrot
docker-compose build --build-arg USER_ID=$(id -u) --build-arg GROUP_ID=$(id -g) bp
docker-compose up -d
docker-compose exec bp su - build

Then follow the Tire Kick directions above starting with "cd black-parrot" or the "Full" directions below. The repo directory will be mounted inside the container.

Getting Started for Real

Users who want to fully evaluate BlackParrot, or develop hardware or software using it should follow Getting Started (Full).

Although the information in collected in this repo, it's recommended to look at these Slides for a quick overview of BlackParrot.

How to Contribute

We welcome external contributions! Please join our mailing list at Google Groups and follow us on Twitter to discuss, ask questions or just tell us how you're using BlackParrot! For a smooth contribution experience, take a look at our Contribution Guide.

Coding Style

BlackParrot is written in standard SystemVerilog, using a subset of the language known to be both synthesizable and compatible with a wide variety of vendor tools. Details of these style choices both functional and aesthetic can be found in our Style Guide

Software Developer Guide

BlackParrot is Linux-capable, so it is possible to run all programs which run on BusyBox. However, for more targeted benchmarks which don't want O/S management overheads (or the overheads of a long Linux boot time in simulation!), it is preferable to write for bare-metal. Additionally, some platform-specific features are only available at the firmware level. Developers looking to write low-level BlackParrot code, or optimize for the BlackParrot platform should look at our SW Developer Guide

Interface Specification

BlackParrot is an aggresively modular design: communication between the components is performed over a set of narrow, latency-insensitive interfaces. The interfaces are designed to allow implementations of the various system components to change independently of one another, without worrying about cascading functional or timing effects. Read more about BlackParrot's standardized interfaces here: Interface Specification

BedRock Coherence System Guide

The BedRock coherence system maintains cache coherence between the BlackParrot processor cores and attached coherent accelerators in a BlackParrot multicore system. Please see the BedRock Guide for more details on the coherence protocol and system.

Microarchitecture Guide

Microarchitecture Guide

Platform Guide

Platform Guide

CAD Backend Guide

A key feature of using BlackParrot is that it has been heavily validated in both silicon and FPGA implementations. All BlackParrot tapeouts and FPGA environments can be found at BlackParrot Examples. Taped out BlackParrot yourself and want to share tips and tricks? Let us know and we can add it to the collection! Looking to implement BlackParrot in a physical system? Take a look at our CAD Backend Guide.

Continuous Integration

Upon commit to the listed branch, a functional regression consisting of full-system tests and module level tests is run and checked for correctness. Additionally, the design is checked with Synopsys DC to verify synthesizability. Work is in progress to continuously monitor PPA.

Help us out

Our goal with BlackParrot is to bootstrap a community-maintained RISC-V core, and we would love for you to get involved. Here are a few starter projects you could do to get your feet wet! Contact us more for details.

  • Our integer divider could be parameterized to do 2 or more cycles per iteration. (Note: Currently somebody is working on this.)
  • Add a parameter to enable / disable FPU logic (including register file, bypass paths, FP divider and FMAC, etc.)
  • Improve the mapping to FPGA
    • We use a portability layer for FPGA that can be optimized, e.g.,
    • BlackParrot uses some SRAMs that use write bit-masks, which are commonly used in ASICs. Our current mapping for FPGA could be made more efficient, reducing LUT usage.
    • Other mappings, such the multiplier to DSP48, could be improved.
    • We have not looked at frequency tuning BP for FPGA at all. The ideal changes would not result in much ASIC/FPGA code bifurcation.
  • We always appreciate pull requests to fix bugs in the documentation, or bug reports that instructions don't work correctly.
  • The RISC-V GCC compiler has some inefficiencies that we have identified, if you have compiler experience you could raise the benchmark numbers for all RISC-V cores versus other ISA's!
  • Our current L2 cache implementation (bsg_cache) is blocking. We would like a non-blocking implementation that supports the same interface and features as the current one, so that can be a configuration option for BlackParrot. It may even be possible to reuse the current code. Contact us to discuss possible implementation approaches!
  • Build a cool demonstration platform with interesting I/O devices using the $129 Arty S7-50 FPGA.


If used for academic research, please cite:

D. Petrisko, F. Gilani, M. Wyse, D. C. Jung, S. Davidson, P. Gao, C. Zhao, Z. Azad, S. Canakci, B. Veluri, T. Guarino, A. J. Joshi, M. Oskin, M. B. Taylor, "BlackParrot: An Agile Open Source RISC-V Multicore for Accelerator SoCs," in IEEE Micro Special Issue on Agile and Open-Source Hardware, July/August, 2020. doi: 10.1109/MM.2020.2996145

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