Scala Python
Latest commit 31bd5c7 Dec 13, 2016 @ccelio ccelio [tage] add "is_degrading" to ubits.
Allows u-bits to take many cycles to degrade, but prevent TAGE from
trying to fire off new degrade() signals until completed.

The Berkeley Out-of-Order RISC-V Processor

This is the source repository for the RV64G RISC-V superscalar Berkeley Out-of-Order Machine (BOOM), written in the Chisel hardware construction language. BOOM is a synthesizable core that targets ASIC processes. It can run on an FPGA (50 MHz on a zc706), but optimizing it to be an FPGA soft-core is a non-goal.

Feature BOOM
Floating Point (IEEE 754-2008)
Atomic Memory Op Support
Viritual Memory
Boots Linux
Privileged Arch v1.9
External Debug

Google group: (!forum/riscv-boom)

For documentation on BOOM visit (

The wiki may also have more information.


This repository is NOT A SELF-RUNNING repository. To instantiate a BOOM core, please use the Rocket chip generator found in the rocket-chip git repository (


These instructions assume you have already installed the riscv-tools toolchain.

If you have not, follow additional instructions below.


To build a BOOM Verilator emulator and run BOOM through a couple of simple tests:

   $ git clone
   $ cd rocket-chip
   $ git checkout boom
   $ git submodule update --init
   $ cd emulator; make run CONFIG=BOOMConfig

There are many BOOM configurations to choose from (and modify!). If you would like to run the Rocket processor, you will need to supply the Rocket configuration and project configuration:

   $ cd emulator; make run CONFIG=DefaultConfig CFG_PROJECT=rocketchip

In the boom branch, the CONFIG variable defaults to BOOMConfig and the CFG_PROJECT variable defaults to boom.

Installing the RISC-V Toolchain

The following (modified) instructions will also build the RISC-V toolchain (if you have not already do so). You will need to set the $RISCV environment variable (where the toolchain will be installed) and you will need to add $RISCV/bin to your $PATH.

   $ export RISCV=/path/to/install/riscv/toolchain
   $ export PATH="${PATH}:$RISCV/bin"
   $ git clone
   $ cd rocket-chip
   $ git checkout boom
   $ git submodule update --init
   $ cd riscv-tools
   $ git submodule update --init --recursive
   $ ./
   $ cd ../emulator; make run CONFIG=BOOMConfig

For more detailed information on the toolchain, visit the riscv-tools repository.

Using the gem5 O3 Pipeline Viewer with BOOM

The O3 Pipeline Viewer is an out-of-order pipeline viewer included in the gem5 suite. BOOM is capable of generating traces compatible with the pipeline viewer, which is useful for understanding what causes pipeline stalls and flushes.

To generate gem5 compatible traces, first set O3PIPEVIEW_PRINTF in boom/src/main/scala/consts.scala to true:

val O3PIPEVIEW_PRINTF = true  // dump trace for O3PipeView from gem5

Rebuild and rerun BOOM. You should find the traces (*.out) in emulator/output/. To generate the visualization run:

   $ boom/util/ -f <TRACE_FILE> > cleaned_trace.out
   $ path_to_gem5/util/ --color --store_completions -o pipeview.out cleaned_trace.out

You can view the visualization by running:

   $ less -r pipeview.out

For more details (and to download, visit the gem5 wiki.

More Info


The RISC-V privileged ISA, platform, and Debug specs are still in flux. BOOM will do its best to stay up-to-date with it!

BOOM is a work-in-progress and remains in active development.


To be filled in as questions are asked...