openpower-isa by libre-soc

Parser of the OpenPOWER ISA, python-based OpenPOWER simulator, and unit tests for POWER hardware, soft-cores and emulators

OpenPOWER ISA resources

OpenPOWER ISA resources, including a python-based simulator plus thousands of OpenPOWER ISA unit tests. Includes machine-readable versions of the OpenPOWER v3.0B specification, from which the python-based simulator is compiled (python-ply) into python. Additional languages (c, c++) are planned. Also planned: co-simulation of power-gem5, microwatt, and other HDL and emulators.

Part of the Libre-SOC Project ( Sponsored by


Prerequisites: qemu, powerpc64-linux-gnu-gcc and associated binutils and gdb, pygdbmi, nmigen and nmutil are needed. Make life easy: use debian, and the following scripts:

Once those are sorted, installation and setup is as follows:

  • python3 develop
  • make svanalysis
  • make pywriter


Usage depends on what your goal is. The python-based simulator is in no way intended to win any speed contests: it's designed for "readability". Additionally, running qemu via pygdmi and extracting its register file is equally horribly slow. To demonstrate, run the following:

python3 openpower/simulator/

This will do the following:

  • compile each of the (tiny) programs in the test
  • extract the raw binary
  • fire up the python-based simulator (ineptly named ISACaller)
  • fire up qemu using the machine interface pygdbmi
  • single-step through both ISACaller and qemu, extracting full regfiles and memory
  • compare them both and throw exceptions on detected discrepancies

This should be pretty obvious as to why this is done: it's checking one simulator against another (and has found bugs in qemu as a result).

What if you could then also run the same unit tests against your own hardware, or against say Microwatt, or Libre-SOC, or against your own emulator?

Given that this is a work-in-progress, so far the only external HDL that uses these unit tests is Libre-SOC's very simple TestIssuer:;a=blob;f=src/soc/simple/test/

The ISACaller itself of course needed to bootstrap up by having unit tests that explicitly and clearly checked against expected values. Example:

  • python openpower/decoder/isa/

These tests pre-prepare the register files, then check afterwards that the result of operation is as expected. In this way, at least basic functionality of ISACaller can be confirmed in a stand-alone fashion (useful if you do not wish to install qemu etc. etc. etc.)


Contributions are welcomed as this is a collaborative Libre Project. Libre-SOC is covered by the following dead-simple Charter:

Contributions even to the Charter, in the form of appropriate Dilbert cartoons especially appreciated:


All programs are written by Libre-SOC team members are LGPLv3+. However the specification and the CSV files came from their respective Copyright holders (IBM, OpenPOWER Foundation, Microwatt)

Other Unit Tests

There do exist other unit tests for OpenPOWER. List them here:

Project Meta

  • Registered on LibreCores 3 days ago
  • Project started 14 days ago
  • Last commit 3 days ago



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0.0.1 is is the only release.

  • 0.0.1
    Apr 24, 2021 e86d9d1



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Last activity 3 days ago
0.0.1 released 13 days ago
Primary language: Python
88 commits by 3 contributors
Luke Kenneth Casson Leighton Cesar Strauss Jacob Lifshay

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