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Ibex is a small 32 bit RISC-V CPU core (RV32IMC/EMC) with a two stage pipeline, previously known as zero-riscy.
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Ibex RISC-V Core

Ibex is a small and efficient, 32-bit, in-order RISC-V core with a 2-stage pipeline that implements the RV32IMC instruction set architecture.

Ibex offers several configuration parameters to meet the needs of various application scenarios. The options include two different choices for the architecture of the multiplier and divider unit, as well as the possibility to drop the support for the "M" extension completely. In addition, the "E" extension can be enabled when opting for a minimum-area configuration.

This core was initially developed as part of the PULP platform under the name "Zero-riscy" [1], and has been contributed to lowRISC who maintains it and develops it further. It is under active development, with further code cleanups, feature additions, and test and verification planned for the future.


The Ibex user manual can be read online at ReadTheDocs. It is also contained in the doc folder of this repository.


We highly appreciate community contributions. To ease our work of reviewing your contributions, please:

  • Create your own branch to commit your changes and then open a Pull Request.
  • Split large contributions into smaller commits addressing individual changes or bug fixes. Do not mix unrelated changes into the same commit!
  • Write meaningful commit messages. For more information, please check out the contribution guide.
  • If asked to modify your changes, do fixup your commits and rebase your branch to maintain a clean history.

When contributing SystemVerilog source code, please try to be consistent and adhere to our Verilog coding style guide.

To get started, please check out the "Good First Issue" list.

Issues and Troubleshooting

If you find any problems or issues with Ibex or the documentation, please check out the issue tracker and create a new issue if your problem is not yet tracked.


Do not hesitate to contact us, e.g., on our public Ibex channel on Zulip!


Unless otherwise noted, everything in this repository is covered by the Apache License, Version 2.0 (see LICENSE for full text).


  1. Schiavone, Pasquale Davide, et al. "Slow and steady wins the race? A comparison of ultra-low-power RISC-V cores for Internet-of-Things applications." 27th International Symposium on Power and Timing Modeling, Optimization and Simulation (PATMOS 2017)
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