Ibex development started in 2015 under the name “Zero-riscy” as part of the PULP platform for energy-efficient computing. Much of the code was developed by simplifying the RV32 CPU core “RI5CY” to demonstrate how small a RISC-V CPU core could actually be [1]. To make it even smaller, support for the “E” extension was added under the code name “Micro-riscy”. In the PULP ecosystem, the core is used as the control core for PULP, PULPino and PULPissimo.

In December 2018 lowRISC took over the development of Zero-riscy and renamed it to Ibex.


  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)