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Dynamically Allocated Neural Network Accelerator for the RISC-V Rocket Microprocessor in Chisel

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Dynamically Allocated Neural Network (DANA) Accelerator

A Chisel3 implementation of a fully connected neural network accelerator, DANA, supporting inference or learning. DANA follows a transactional model of computation supporting simultaneous multithreading of transactions [1]. DANA integrates with the RISC-V Rocket microprocessor as a Rocket Custom Coprocessor (RoCC).

This is currently compatibile with rocket-chip:f3299ae9 -- an older rocket-chip version used by fpga-zynq.

tl;dr: Setup

This is compatible with ucb-bar/fpga-zynq:f03982e. Clone this repo, add DANA, and build:

# Clone fpga-zynq
git clone $fpga_zynq_dir
cd $fpga_zynq_dir
git reset --hard f03982e
git submodule update --init rocket-chip testchipip

Add DANA to rocket-chip

cd $fpga_zynq_dir/rocket-chip git submodule update --init git clone cd $fpga_zynq_dir/rocket-chip/dana git submodule update --init

Build an emulator

cd $fpga_zynq_dir/rocket-chip/emulator make ROCKETCHIP_ADDONS=dana CONFIG=DanaEmulatorConfig

Build example DANA networks in 'dana/build/nets'

cd $fpga_zynq_dir/rocket-chip/dana make

Build bare metal tests for DANA in 'dana/tests/build'

cd $fpga_zynq_dir/rocket-chip/riscv-tools git submodule update --init --recursive riscv-tests cd $fpga_zynq_dir/rocket-chip/dana/tests autoconf mkdir build cd build ../configure make

Run tests on the emulator with or without printfs

cd $fpga_zynq_dir/rocket-chip/emulator ./emulator-rocketchip-DanaEmulatorConfig
../dana/tests/build/nets/xfiles-dana-nets-p-xorSigmoidSymmetric ./emulator-rocketchip-DanaEmulatorConfig
2>&1 |
spike-dasm |
tee xfiles-dana-nets-p-xorSigmoidSymmetric.log

To build Verilog suitable for Zynq FPGAs (Zedboard, ZC706):

# Add a Zedboard configuration to fpga-zynq
echo "class DanaZedboardConfig extends Config (
  new rocketchip.HasDanaRocc ++
  new xfiles.DefaultXFilesConfig ++
  new dana.DanaConfig(
    numPes     = 2,
    cache      = 1,
    cacheSize  = 512 * 1024,
    scratchpad =  16 * 1024) ++
    new dana.DefaultDanaConfig ++
    new ZynqConfig)" >> $fpga_zynq_dir/common/src/main/scala/Configs.scala

Build for the FPGA (Zedboard)

cd $fpga_zynq_dir/zedboard make rocket ROCKETCHIP_ADDONS=dana CONFIG=DanaZedboardConfig make project ROCKETCHIP_ADDONS=dana CONFIG=DanaZedboardConfig make fpga-images-zedboard/boot.bin CONFIG=DanaZedboardConfig

Table of Contents


Requirements: *

python 3.X
* All dependencies needed for the RISC-V toolchain

1) Clone the Rocket Chip Repository

This is not, at present, a standalone repository and must be cloned inside of an existing Rocket Chip clone. The following will grab a supported version of rocket-chip and clone DANA inside of it:

git reset --hard f3299ae91d3f01d0349eb4746886e303e8fb1b41
git submodule update --init --recursive
git clone
cd dana
git submodule update --init

2) Build the RISC-V Toolchain

This requires a supported version of the RISC-V toolchain. Go ahead and build the version of the toolchain pointed at by the rocket-chip repository. This requires setting the

environment variable and satisfying any dependencies required to build the toolchain.
cd $ROCKETCHIP_DIR/riscv-tools

Emulation (Functional Verification)

This project uses Chisel3 and FIRRTL for hardware design and Verilog generation.

Rocket Chip Emulation

You can build a complete version of Rocket Chip that includes DANA in a RoCC socket.

You can build an emulator of Rocket + DANA using the rocket-chip make target inside the rocket-chip/emulator directory. The Makefile just needs to know what configuration we're using and that we have additional Chisel code located in the

cd $ROCKETCHIP/emulator
make CONFIG=DanaEmulatorConfig ROCKETCHIP_ADDONS=dana

We provide bare-metal test programs inside the tests directory.

Emulation Debugging

For debugging or running the emulator more verbosely, you have the option of either relying on Chisel's

or building a version of the emulator that supports full VCD dumping.
Printf Debugging


writes to STDERR, all
statements are disabled by default. You can enable all Chisel-included
commands with the
cd $ROCKETCHIP/emulator
./emulator-Top-DanaEmulatorConfig +verbose [binary] 2>&1 | tee run.log

Note: Rocket Chip dumps information every cycle and it is often useful to grep for the exact

that you're looking for.
Waveform Debugging

You can build a "debug" version of the emulator (which provides full support for generating vcd traces with:

cd $ROCKETCHIP/emulator
make debug

This creates a

emulator which supports a
option for generating a VCD file, a
option for starting VCD dumping at a specific cycle.

To further reduce the size of the VCD file we provide a tool that prunes a VCD file to only include signals in a specific module and it's children,

. Example usage to only emit DANA signals:

cd $ROCKETCHIP_DIR/emulator
./emulator-Top-DanaEmulatorConfig-debug -v- [binary] 2>&1 | ../dana/util/hdl-tools/scripts/vcd-prune -m Dana > run.vcd

This waveform can then be viewed using GTKWave by building GTKWave locally and using a helper script to pre-populate the waveform window:

cd $ROCKETCHIP/emulator
make -C ../dana/util/hdl-tools gtkwave
../dana/util/hdl-tools/scripts/gtkwave-helper run.vcd

Hardware Evaluation

Rocket + DANA can be evaluated on a Zynq FPGA using the Berkeley-provided


Known Issues and WIP Features

There are a few remaining things that we're working on closing out which limit the set of available features.

Configuration Size

Currently, the neural network configuration must fit completely in one of DANA's configuration cache memories. DANA's neural network configuration format using 32-bit internal pointers meaning that networks up to 4GiB are theoretically supported. We've used networks up to 512KiB in size on FPGA without issue.

Linux Support

We're working on a full integration of the X-FILES supervisor library with the Linux kernel. Supervisor features are currently supported via system calls added to the RISC-V Proxy Kernel via an included patch.

IO Queues

While neural network configurations are loaded from the memory of the microprocessor, all input and output data is transferred from Rocket to DANA hardware through the Rocket Custom Coprocessor (RoCC) register interface. We have plans to enable asynchronous transfer through in-memory queues.

Additional Documentation

Additional documentation can be found in the

directory or in some of our publications.


If you use this for research, please cite the original PACT paper:

  author    = {Schuyler Eldridge and
               Amos Waterland and
               Margo Seltzer and
               Jonathan Appavoo and
               Ajay Joshi},
  title     = {Towards General-Purpose Neural Network Computing},
  booktitle = {2015 International Conference on Parallel Architecture and Compilation,
               {PACT} 2015, San Francisco, CA, USA, October 18-21, 2015},
  pages     = {99--112},
  year      = {2015},
  url       = {},
  doi       = {10.1109/PACT.2015.21},
  timestamp = {Wed, 04 May 2016 14:25:23 +0200},
  biburl    = {},
  bibsource = {dblp computer science bibliography,}

Doc Directory

Specific documentation includes: * Binary Encodings and Data Structures * Debugging * FPGA Setup * Timing * Toolflow * U-Boot


[1] S. Eldridge, A. Waterland, M. Seltzer, J. Appavoo, and A. Joshi, "Towards General Purpose Neural Network Computing", in Proceedings of the International Conference on Parallel Architectures and Compilation Techniques (PACT). 2015. * Paper * Presentation

[2] S. Eldridge, "Neural Network Computing Using On-Chip Accelerators", Boston University. 2016. * Thesis

Workshop Presentations and Posters

[3] S. Eldridge., T. Unger, M. Sahaya Louis, A. Waterland, M. Seltzer, J. Appavoo, and A. Joshi, "Neural Networks as Function Primitives: Software/Hardware Support with X-FILES/DANA", Boston Area Architecture Workshop (BARC). 2016. * Paper * Presentation * Poster

Contributors and Acknowledgments

The following people, while not mentioned in the commit log, have contributed directly or indirectly to the development of this work: * Jonathan Appavoo * Amos Waterland * Tommy Unger * Han Dong * Leila Delshad Tehrani

This work was funded by a NASA Space Technology Research Fellowship.

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