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This is a fork of the PULP Platform RI5CY core for Verilator and GDB server development. All essential parts developed in here have been merged back and are available in the upstream repository.

RI5CY is a small 4-stage RISC-V core. It starte its life as a fork of the OR10N cpu core that is based on the OpenRISC ISA.

RI5CY fully implements the RV32I instruction set, the multiply instruction from RV32M and many custom instruction set extensions that improve its performance for signal processing applications.

The core was developed as part of the PULP platform for energy-efficient computing and is currently used as the processing core for PULP and PULPino.


A datasheet that explains the most important features of the core can be found in docs/datasheet/.

It is written using LaTeX and can be generated as follows

make all

Verilator model

The Verilator model can be built at the top level using

make all

The RI5CY code uses some quite advanced System Verilog, so you will need a very up to date Verilator. We succeeded with development version 3.905, but found version 3.900 crashed.


The upstream design is all licensed under the SolderPad License v 0.51, see the file LICENSE.solderpad.

The modifications by Embecosm to support Verilator modeling and implement a GDB server are licensed under the GNU General Public License 3.0, see the file LICENSE.GPL3.

The headers for source files should indicate which license applies. If no license is specified, then the solderPad license should be assumed.


The PULP RI5CY core modified for Verilator modeling and as a GDB server.




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