|Designer||Damjan Lampret, with contributions from others in the OpenRISC community|
|Endianness||Big (unimplemented stub for Little)|
|General purpose||16 or 32|
OpenRISC is a project to develop a series of open source instruction set architectures based on established reduced instruction set computing (RISC) principles. It is the original flagship project of the OpenCores community.
The first (and currently only) architectural description is for the OpenRISC 1000, describing a family of 32 and 64-bit processors with optional floating point and vector processing support, and the OpenRISC 1200 implementation of this was designed by Damjan Lampret in 2000, written in the Verilog hardware description language.
A reference SoC implementation based on the OpenRISC 1200 was developed, known as ORPSoC (the OpenRISC Reference Platform System-on-Chip). A number of groups have demonstrated ORPSoC and other OR1200 based designs running on FPGAs, and there have been a number of commercial derivatives produced.
OpenCores has always been a commercially owned organization. In 2015, the core active users of OpenCores established the independent Free and Open Source Silicon Foundation (FOSSi), and registered the libreCores.org website, as the basis for all future development, independent of commercial control.
The instruction set is a reasonably simple MIPS-like traditional RISC using a 3-operand load-store architecture, with 16 or 32 general-purpose registers and a fixed 32-bit instruction length. The instruction set is mostly identical between the 32 and 64 bit versions of the specification, the main difference being the register width (32 or 64 bits) and page table layout. The OpenRISC specification includes all features common to modern desktop/server processors: a supervisor mode and virtual memory system, optional read, write and execute control for memory pages, and instructions for synchronization and interrupt handling between multiple processors.
Another notable feature is a rich set of SIMD instructions intended for digital signal processing.
Most implementations are on FPGAs which give the possibility to iterate on the design at the cost of performance.
As the OpenRISC 1000 is now considered stable, ORSoC (owner of OpenCores) launched a crowd-funding project trying to build a cost-efficient ASIC to get improved performance. ORSoC faced criticism for this from the community. The project never reached the goal.
As of April 2017, no open-source ASIC has been produced yet.
Several commercial organizations have developed derivatives of the OpenRISC 1000 architecture, including the ORC32-1208 from ORSoC and the BA12, BA14 and BA22 from Beyond Semiconductor. Dynalith Systems provide the iNCITE FPGA prototyping board, which is capable of running both the OpenRISC 1000 and BA12. Flex and Jennic Limited manufactured the OpenRISC as part of an ASIC. Samsung use the OpenRISC 1000 in their DTV system-on-chips (SDP83 B-Series, SDP92 C-Series, SDP1001/SDP1002 D-Series, SDP1103/SDP1106 E-Series). Allwinner Technology are reported to use an OpenRISC core in their AR100 power controller, which forms part of the A31 ARM-based SoC.
TechEdSat, the first NASA OpenRISC architecture based Linux computer launched in July 2012, and was deployed in October 2012 to the International Space Station with hardware provided, built, and tested by ÅAC Microtec and ÅAC Microtec North America.
Academic and non-commercial use
The OpenRISC community have ported the GNU toolchain to OpenRISC to support development in C and C++. Using this toolchain the newlib, uClibc, musl (as of release 1.1.4) and glibc libraries have been ported to the processor. Dynalith provides OpenIDEA, a graphical development environment based on this toolchain. A project to port LLVM to the OpenRISC 1000 architecture started in early 2012 (project page).
The OR1K project provides an instruction set simulator, or1ksim. The flagship implementation, the OR1200, is a register-transfer level (RTL) model in Verilog HDL, from which a SystemC-based cycle-accurate model can be built in ORPSoC. A high speed model of the OpenRISC 1200 is also available through the Open Virtual Platforms (OVP) initiative set up by Imperas.
Operating system support
The mainline Linux kernel gained support for OpenRISC in version 3.1. The implementation merged in this release is the 32-bit OpenRISC 1000 family (or1k). Previously OpenRISC 1000 architecture, but this has now been superseded by the mainline port.
- Amber (processor core), ARM-Compatible OpenCores Project
- Free and Open Source Silicon Foundation
- OpenRISC 1200
- OVPsim, Open Virtual Platforms
- Damjan Lampret et al., "OpenRISC 1000 Architecture Manual", Architecture Version 1.0, Document Revision 0, December 5, 2012. Available from the OpenCores website 
- Interview with OpenRISC designer Damjan Lampret, published online in EE Times in February 2000 
- Interview with OpenRISC designer Damjan Lampret, on the cover of February 2000 edition of EE Times
- Patrick Pelgrims, Tom Tierens and Dries Driessens, "Basic Custom OpenRISC System Hardware Tutorial: Embedded system design based upon Soft- and Hardcore FPGA’s", De Nayer Instituut, Hogeschool voor Wetenschap & Kunst, 2004. Available online 
- Xiang Li and Lin Zuo, "Open source embedded platform based on OpenRISC and DE2-70", Masters dissertation, SoC program, KTH, Sweden. Available online 
- Samsung Open Source Release Center, follow the links → TV & VIDEO → TV → DTV → ETC → OR1200.zip
- Linux-sunxi project community wiki page on the AR100 controller. Retrieved on 20 July 2013.
- UVM Reference Flow, Accellera website (undated).
- Post to the openrisc mailing lists at lists.openrisc.net on 8 April 2012 by Fredrick Bruhn, CEO of ÅAC Microtec
- Press release 11 October 2012, ÅAC Microtec AB.
- Multicore Architecture and Programming Model Co-Optimization (MAPCO), Stefan Wallentowitz, Thomas Wild and Andreas Herkersdorf. Research poster at the Sixth International Summer School on Advanced Computer Architecture and Compilation for High-Performance and Embedded Systems (ACACES), Terrassa (Barcelona), Spain, 11–17 July 2010.
- Chips (Programmable Logic, Computer Conservation with FPGAs, OpenCores & OpenRISC 1000). OSHUG meeting #9, Skills Matter, 116-120 Goswell Road, London, 21 April 2011.
- Practical System-on-Chip (Program your own open source FPGA SoC). OSHUG meeting #17, Centre for Creative Collaboration, 16 Acton Street, London, 29 March 2012.
- OpenRISC 1200 soft processor. Blog post by Sven-Åke Andersson, 2 March 2012.
- Comparing four 32-bit soft processor cores. Clive Maxfield, EE Times, 3 May 2012.
- "git.kernel.org - linux/kernel/git/torvalds/linux-2.6.git/tree - arch/openrisc/". git.kernel.org. Retrieved 2011-10-17.
- "Linux 3.1". Kernel Newbies. Retrieved 2011-10-17.
- QEMU Changelog 1.2
- Official website
- Open Source Semiconductor Core Licensing, 25 Harvard Journal of Law & Technology 131 (2011) Article analyzing the law, technology and business of open source semiconductor cores
- Beyond Semiconductor commercial fabless semiconductor company founded by the developers of OpenRISC
- Dynalith Systems company website.
- Imperas company website.
- Flex company website
- Jennic company website
- Eetimes article
- OpenRISC tutorial