Several implementations of the OpenRISC architecture exist. In the following we will summarize the most well known.

Harware Implementations

The hardware implementations are full processor implementations written in an Hardware Description Language. Such a description is either the input to a hardware synthesis, such as for an ASIC or an FPGA, or for an RTL simulation.

Nevertheless, the processor cores are for themselves not running on their own, but are complex IP blocks that at least need a clock and reset signal and some memories connected to them. You can use one of the popular system-on-chip to try out the processor cores.


OR1200 is the original implementation of the OpenRISC 1000 architecture.

The source code can be found on github at openrisc/or1200.


The mor1kx is pretty much a drop in replacement for the original or1200 processor but it has its advantages.

  • It follows, in our opinion, better coding standards compared to the or1200
  • It is licensed under the OHDL which is suited for open hardware
  • It implementation is highly reconfigurable allowing to be resized to meet target sixe and performance requirements.
  • It has docs that explain even more

In 2014 the author, Julius Baxter, gave the following presentation about mor1kx which goes into detail about the motivation for the processor rewrite and architecture.

The source code can be found on github at openrisc/mor1kx

To build a system with mor1kx have a look at the some of the hardware tutorials or have a look at some of the systems available in orpsoc-cores which can be built with FuseSoC.

System Simulators


Or1ksim is a generic OpenRISC 1000 architecture simulator capable of emulating OpenRISC based computer systems at the instruction level. It includes models of a range of peripherals, allowing complete systems to be modelled.


QEMU is a cpu emulator that supports many cpu targets. OpenRISC has been supported since version 1.2.