View source for Soft microprocessor

{{Short description|Microprocessor design embeddable in other computer systems}}
{{Use American English|date = April 2019}}
{{missing information||three [[OpenPOWER]] cores, one Moxie core, both at RTL level|date=July 2020}}
A '''soft microprocessor''' (also called softcore microprocessor or a '''soft processor''') is a [[microprocessor]] core that can be wholly implemented using [[logic synthesis]]. It can be implemented via different [[semiconductor]] devices containing programmable logic (e.g., [[Field-programmable gate array|FPGA]], [[Complex programmable logic device|CPLD]]), including both high-end and commodity variations.<ref>{{usurped|1=[https://web.archive.org/web/20181013095941/http://www.dailycircuitry.com/2011/10/zet-soft-core-running-windows-30.html Article title]}}
"Zet soft core running Windows 3.0" by Andrew Felch 2011</ref>

Most systems, if they use a soft processor at all, only use a single soft processor. However, a few designers tile as many soft cores onto an FPGA as will fit.<ref>
{{cite web |url=http://www.embedded.com/columns/showArticle.jhtml?articleID=192700615 |title=Embedded.com - FPGA Architectures from 'A' to 'Z' : Part 2 |access-date=2012-08-18 |url-status=dead |archive-url=https://web.archive.org/web/20071008163016/http://www.embedded.com/columns/showArticle.jhtml?articleID=192700615 |archive-date=2007-10-08 }}
"FPGA Architectures from 'A' to 'Z'" by Clive Maxfield 2006
</ref> In those [[multi-core]] systems, rarely used resources can be shared between all the cores in a cluster.

While many people put exactly one soft microprocessor on a FPGA, a sufficiently large FPGA can hold two or more soft microprocessors, resulting in a [[multi-core processor]]. The number of soft processors on a single FPGA is limited only by the size of the FPGA.<ref>[http://www.xilinx.com/products/design_resources/proc_central/microblaze_faq.pdf MicroBlaze Soft Processor: Frequently Asked Questions] {{webarchive|url=https://web.archive.org/web/20111027074459/http://www.xilinx.com/products/design_resources/proc_central/microblaze_faq.pdf |date=2011-10-27 }}</ref> Some people have put dozens or hundreds of soft microprocessors on a single FPGA.<ref>
István Vassányi.
"Implementing processor arrays on FPGAs". 1998.
[https://doi.org/10.1007%2FBFb0055278 ]
</ref><ref>
Zhoukun WANG and Omar HAMMAMI.
"A 24 Processors System on Chip FPGA Design with Network on Chip".
[http://www.design-reuse.com/articles/21583/processor-noc-fpga.html]
</ref><ref>
John Kent.
"Micro16 Array - A Simple CPU Array"
[http://members.optusnet.com.au/jekent/Micro16Array/index.html]
</ref><ref>
Kit Eaton.
"1,000 Core CPU Achieved: Your Future Desktop Will Be a Supercomputer".
2011.
[http://www.fastcompany.com/1714174/1000-core-cpu-achieved-your-future-desktop-will-be-a-supercomputer?partner=rss]
</ref><ref>
"Scientists Squeeze Over 1,000 Cores onto One Chip".
2011.
[http://www.ecnmag.com/news/2011/01/research/Over-1000-Cores-on-One-Chip.aspx] {{Webarchive|url=https://web.archive.org/web/20120305082424/http://www.ecnmag.com/news/2011/01/research/Over-1000-Cores-on-One-Chip.aspx |date=2012-03-05 }}
</ref> This is one way to implement [[Massively parallel|massive parallelism]] in computing and can likewise be applied to [[In-memory processing|in-memory computing]].

A soft microprocessor and its surrounding peripherals implemented in a FPGA is less vulnerable to obsolescence than a discrete processor.<ref>{{Cite web
 | author=Joe DeLaere.
 | url=https://www.altera.com/content/dam/altera-www/global/en_US/pdfs/literature/wp/wp-01255-top-7-reasons-to-replace-your-microcontroller-with-a-max-10-fpga.pdf 
 | title="Top 7 Reasons to Replace Your Microcontroller with a MAX 10 FPGA"}}
</ref><ref>{{Cite web
 |author1=John Swan |author2=Tomek Krzyzak.
 | url=http://www.embedded.com/print/4015159 
 | title="Using FPGAs to avoid microprocessor obsolescence"
 | date=2008
 | archive-url=https://web.archive.org/web/20161013004106/http://www.embedded.com/print/4015159
 | archive-date=2016-10-13
}}</ref><ref>
{{Cite web|url=https://www.electronicsweekly.com/news/products/fpga-news/fpga-processor-ip-needs-to-be-supported-2010-02/|title=FPGA processor IP needs to be supported|last=Staff|date=2010-02-03|website=Electronics Weekly|language=en-GB|access-date=2019-04-03}}
</ref>

== Core comparison ==

{| class="wikitable sortable"
|-
! Processor
! Developer
! Open source
! Bus support
! Notes
! Project home
! Description language
|-
| colspan="7" align="center" | ''based on the [[ARM architecture|ARM]] instruction set architecture''
|-
| [[Amber (processor core)|Amber]]
| Conor Santifort
| {{yes|LGPLv2.1}}
| [[Wishbone (computer bus)|Wishbone]]
| [[ARM architecture|ARMv2a]] 3-stage or 5-stage pipeline
| [https://opencores.org/project/amber Project page at Opencores]
| Verilog
|-
| [[Cortex-M1]]
| [[ARM Holdings|ARM]]
| {{no}}
| [http://www.arm.com/products/system-ip/interconnect/index.php]
| 70–200{{nbsp}}MHz, 32-bit RISC
| [http://www.arm.com/products/CPUs/ARM_Cortex-M1.html]
| Verilog
|-
| colspan="7" align="center" | ''based on the [[AVR microcontrollers|AVR]] instruction set architecture''
|-
| Navré
| Sébastien Bourdeauducq
| {{yes}}
| Direct SRAM
| [[Atmel AVR]]-compatible 8-bit RISC
| [http://opencores.org/project,navre Project page at Opencores]
| Verilog
|-
| pAVR
| Doru Cuturela
| {{yes}}
|
| [[Atmel AVR]]-compatible 8-bit RISC
| [http://opencores.org/project,pavr Project page at Opencores]
| VHDL
|-
| softavrcore
| Andras Pal
| {{yes}}
| Standard AVR buses (core-coupled I/O, synchronous SRAM, synchronous program ROM)
| [[Atmel AVR]]-compatible 8-bit RISC (up to AVR5), peripherals and SoC features included
| [http://opencores.org/project/softavrcore Project page at Opencores]
| Verilog
|-
| colspan="7" align="center" | ''based on the [[MicroBlaze]] instruction set architecture''
|-
| [[AEMB]]
| Shawn Tan
| {{yes}}
| [[Wishbone (computer bus)|Wishbone]]
| MicroBlaze EDK 3.2 compatible
| [http://www.aeste.my/aemb AEMB]
| Verilog
|-
| [[MicroBlaze]]
| [[Xilinx]]
| {{no}}
| PLB, OPB, FSL, LMB, AXI4
|
| [https://web.archive.org/web/20030430214925/http://www.xilinx.com/microblaze/ Xilinx MicroBlaze]
|
|-
| [[OpenFire Soft Processor|OpenFire]]
| Virginia Tech CCM Lab
| {{yes}}
| OPB, FSL
| Binary compatible with the MicroBlaze
| [https://web.archive.org/web/20090724052731/http://www.ccm.ece.vt.edu/~scraven/openfire.html]<ref>{{Cite web|url=http://opencores.org/project,openfire_core,overview|title=Overview :: OpenFire Processor Core :: OpenCores}}</ref>
| Verilog
|-
| [[SecretBlaze]]
| LIRMM, University of Montpellier / CNRS
| {{yes}}
| [[Wishbone (computer bus)|Wishbone]]
| MicroBlaze ISA, VHDL
| [http://www.lirmm.fr/ADAC/?page_id=462 SecretBlaze]
| VHDL
|-
| colspan="7" align="center" | ''based on the [[MCS-51]] instruction set architecture''
|-
| [http://www.microcorelabs.com MCL51]
| [[MicroCore Labs]]
| {{yes}}
| Ultra-small-footprint microsequencer-based 8051 core
| 312 Artix-7 LUTs. Quad-core 8051 version is 1227 LUTs.
| [http://www.microcorelabs.com MCL51 Core]
|
|-
| [https://web.archive.org/web/20131008041359/http://wiki.altium.com/display/ADOH/TSK51x+MCU TSK51/52]
| [[Altium]]
| {{no|Royalty-free}}
| [[Wishbone (computer bus)|Wishbone]] / [[Intel 8051]]
| 8-bit [[Intel 8051]] instruction set compatible, lower clock cycle alternative
| [https://web.archive.org/web/20160306202550/http://wiki.altium.com/display/adoh/processor-based+fpga+design Embedded Design on Altium Wiki]
|
|-
| colspan="7" align="center" | ''based on the [[MIPS architecture|MIPS]] instruction set architecture''
|-
| [http://www.cl.cam.ac.uk/research/security/ctsrd/beri/ BERI]
| [[University of Cambridge]]
| {{yes|BSD}}
|
| [[MIPS architecture|MIPS]]
| [http://www.cl.cam.ac.uk/research/security/ctsrd/beri/ Project page]
| [[Bluespec]]
|-
| [http://www.dossmatik.de/mais-cpu.html Dossmatik]
| [[René Doss]]
| {{yes|CC BY-NC 3.0, except ''commercial applicants have to pay a licence fee''.}}
| Pipelined bus
| MIPS I instruction set pipeline stages
| [http://www.dossmatik.de/mais-cpu.html Dossmatik]
| VHDL
|-
| [https://web.archive.org/web/20131020113429/http://wiki.altium.com/display/ADOH/TSK3000A TSK3000A]
| [[Altium]]
| {{no|Royalty-free}}
| [[Wishbone (computer bus)|Wishbone]]
| 32-bit [[R3000]]-style RISC modified Harvard-architecture CPU
| [https://web.archive.org/web/20160306202550/http://wiki.altium.com/display/adoh/processor-based+fpga+design Embedded Design on Altium Wiki]
|
|-
| colspan="7" align="center" | ''based on the [[PicoBlaze]] instruction set architecture''
|-
| [[PacoBlaze]]
| Pablo Bleyer
| {{yes}}
|
| Compatible with the PicoBlaze processors
| [http://bleyer.org/pacoblaze PacoBlaze]
| Verilog
|-
| [[PicoBlaze]]
| [[Xilinx]]
| {{no}}
|
|
| [https://web.archive.org/web/20030501203653/http://www.xilinx.com/picoblaze/ Xilinx PicoBlaze]
| VHDL, Verilog
|-
| colspan="7" align="center" | ''based on the [[RISC-V]] instruction set architecture''
|-
| [https://github.com/f32c/f32c f32c]
| University of Zagreb
| {{yes|BSD}}
| AXI, SDRAM, SRAM
| 32-bit, RISC-V / MIPS ISA subsets (retargetable), GCC toolchain
| [https://github.com/f32c/f32c f32c]
| VHDL
|-
| [https://github.com/stnolting/neorv32 NEORV32]
| Stephan Nolting
| {{yes|BSD}}
| Wishbone b4, AXI4
| rv32[i/e] [m] [a] [c] [b] [u] [Zfinx] [Zicsr] [Zifencei], RISC-V-compliant, CPU & SoC available, highly customizable, GCC toolchain
| [https://github.com/stnolting/neorv32 GitHub] [https://opencores.org/projects/neorv32 OpenCores]
| VHDL
|-
| VexRiscv
| SpinalHDL|SpinalHDL
| {{Yes}}
| AXI4 / Avalon
| 32-bit, RISC-V, up to 340{{nbsp}}MHz on Artix 7. Up to 1.44{{nbsp}}DMIPS/MHz.
| https://github.com/SpinalHDL/VexRiscv
| VHDLVerilog (SpinalHDL)
|-
| colspan="7" align="center" | ''based on the [[SPARC]] instruction set architecture''
|-
| [[LEON|LEON2(-FT)]]
| [[European Space Agency|ESA]]
| {{yes}}
| AMBA2
| SPARC V8
| [http://www.esa.int/TEC/Microelectronics/SEMUD70CYTE_0.html ESA]
| VHDL
|-
| [[LEON|LEON3/4]]
| Aeroflex Gaisler
| {{yes}}
| AMBA2
| SPARC V8
| [http://www.gaisler.com/cms/index.php?option=com_content&task=view&id=156&Itemid=104 Aeroflex Gaisler]
| VHDL
|-
| [http://parallel.princeton.edu/openpiton/specs.html OpenPiton]
| Princeton Parallel Group
| {{Yes}}
|
| [[Manycore processor|Manycore]] [[SPARC|SPARC V9]]
| [http://parallel.princeton.edu/openpiton/specs.html OpenPiton]
| Verilog
|-
| [[OpenSPARC|OpenSPARC T1]]
| [[Sun Microsystems|Sun]]
| {{yes}}
|
| 64-bit
| [http://www.opensparc.net/opensparc-t1/index.html OpenSPARC.net]
| Verilog
|-
| Tacus/PIPE5
| TemLib
| {{yes}}
| Pipelined bus
| SPARC V8
| [http://temlib.org TEMLIB]
| VHDL
|-
| colspan="7" align="center" | ''based on the [[x86]] instruction set architecture''
|-
| CPU86
| HT-Lab
| {{yes}}
|
| 8088-compatible CPU in VHDL
| [http://www.ht-lab.com/cpu86.htm cpu86]
| VHDL
|-
| [http://www.microcorelabs.com MCL86]
| [[MicroCore Labs]]
| {{yes}}
| 8088 BIU provided. Others easy to create.
| Cycle accurate 8088/8086 implemented with a microsequencer. Less than 2% utilization of Kintex-7.
| [http://www.microcorelabs.com MCL86 Core]
|
|-
| [https://www.jamieiles.com/80186/ s80x86]
| Jamie Iles
| {{yes|GPLv3}}
| Custom
| 80186-compatible GPLv3 core
| [https://www.jamieiles.com/80186/ s80x86]
| SystemVerilog
|-
| Zet
| Zeus Gómez Marmolejo
| {{yes}}
| [[Wishbone (computer bus)|Wishbone]]
| x86 PC clone
| [https://archive.today/20130112150552/http://zet.aluzina.org/ Zet]
| Verilog
|-
| [[ao486 (hardware)|ao486]]
| Aleksander Osman
| {{yes|3-Clause BSD}}
| Avalon
| i486 SX compatible core
| [https://github.com/alfikpl/ao486 ao486]
| Verilog
|-
| colspan="7" align="center" | ''based on the [[Power ISA|PowerPC/Power]] instruction set architecture''
|-
| [[PowerPC 400#PowerPC 405|PowerPC 405S]]
| IBM
| {{No}}
| [[CoreConnect]]
| 32-bit PowerPC v.2.03 Book E
| [[IBM]]
| Verilog
|-
| [[PowerPC 400#PowerPC 440|PowerPC 440S]]
| IBM
| {{No}}
| [[CoreConnect]]
| 32-bit PowerPC v.2.03 Book E
| [[IBM]]
| Verilog
|-
| [[PowerPC 400#PowerPC 470|PowerPC 470S]]
| IBM
| {{No}}
| [[CoreConnect]]
| 32-bit PowerPC v.2.05 Book E
| [[IBM]]
| Verilog
|-
| [[OpenPower Microwatt|Microwatt]]
| IBM/OpenPOWER
| {{yes|CC-BY 4.0}}
| [[Wishbone (computer bus)|Wishbone]]
| 64-bit PowerISA 3.0 proof of concept
| [https://github.com/antonblanchard/microwatt Microwatt @ Github]
| VHDL
|-
| [[OpenPower Microwatt#Chiselwatt|Chiselwatt]]
| IBM/OpenPOWER
| {{yes|CC-BY 4.0}}
| [[Wishbone (computer bus)|Wishbone]]
| 64-bit PowerISA 3.0
| [https://github.com/antonblanchard/chiselwatt Chiselwatt @ Github]
| Chisel
|-
| [[Libre-SOC]]
| [https://libre-soc.org Libre-SoC.org]
| {{yes|BSD/LGPLv2+}}
| [[Wishbone (computer bus)|Wishbone]]
| 64-bit PowerISA 3.0. CPU/GPU/VPU implementation and custom vector instructions
| [https://libre-soc.org Libre-SoC.org]
| python/nMigen
|-
| [[IBM A2#A2I|A2I]]
| IBM/OpenPOWER
| {{yes|CC-BY 4.0}}
| Custom PBus
| 64-bit PowerPC 2.6 Book E. In order core
| [https://github.com/openpower-cores/a2i A2I @ Github]
| VHDL
|-
| [[IBM A2#A2O|A2O]]
| IBM/OpenPOWER
| {{yes|CC-BY 4.0}}
| Custom PBus
| 64-bit PowerPC 2.7 Book E. Out of order core
| [https://github.com/openpower-cores/a2o A2O @ Github]
| Verilog
|-
| colspan="7" align="center" | ''Other architectures''
|-
| [[ARC (processor)|ARC]]
| [[Synopsys#ARC International|ARC International]], [[Synopsys]]
| {{no}}
|
| 16/32/64-bit ISA RISC
| [https://www.synopsys.com/designware-ip/processor-solutions.html DesignWare ARC]
| Verilog
|-
| ERIC5
| Entner Electronics
| {{no}}
|
| 9-bit RISC, very small size, C-programmable
| [http://www.entner-electronics.com/tl/index.php/eric5.html ERIC5] {{Webarchive|url=https://web.archive.org/web/20160305131214/http://www.entner-electronics.com/tl/index.php/eric5.html |date=2016-03-05 }}
| VHDL
|-
| [https://github.com/howerj/forth-cpu H2 CPU]
| Richard James Howe
| {{yes | MIT}}
| Custom
| 16-bit Stack Machine, designed to execute Forth directly, small
| [https://github.com/howerj/forth-cpu H2 CPU]
| VHDL
|-
| [http://www.fpga-cores.com/instant-soc/ Instant SoC]
| [http://www.fpga-cores.com/ FPGA Cores]
| {{no}}
| Custom
| 32-bit RISC-V M Extension, SoC defined by C++
| [http://www.fpga-cores.com/instant-soc/ Instant SoC]
| VHDL
|-
| [[Java optimized processor|JOP]]
| Martin Schoeberl
| {{yes}}
| [[SimpCon]] / [[Wishbone (computer bus)|Wishbone]] (extension)
| Stack-oriented, hard real-time support, executing [[Java bytecode]] directly
| [https://web.archive.org/web/20190417225405/http://www.jopdesign.com/ Jop]
| VHDL
|-
| [[LatticeMico8]]
| [[Lattice Semiconductor|Lattice]]
| {{yes}}
| [[Wishbone (computer bus)|Wishbone]]
|
| [http://www.latticesemi.com/Products/DesignSoftwareAndIP/IntellectualProperty/IPCore/IPCores02/Mico8.aspx LatticeMico8]
| Verilog
|-
| [[LatticeMico32]]
| [[Lattice Semiconductor|Lattice]]
| {{yes}}
| [[Wishbone (computer bus)|Wishbone]]
|
| [http://www.latticesemi.com/products/intellectualproperty/ipcores/mico32/index.cfm LatticeMico32]
| Verilog
|-
| [https://lxp32.github.io/ LXP32]
| Alex Kuznetsov
| {{yes|MIT}}
| [[Wishbone (computer bus)|Wishbone]]
| 32-bit, 3-stage pipeline, [[register file]] based on block RAM
| [https://lxp32.github.io/ lxp32]
| VHDL
|-
| [https://github.com/MicroCoreLabs/Projects MCL65]
| [[MicroCore Labs]]
| {{yes}}
| Ultra-small-footprint microsequencer-based 6502 core
| 252 Spartan-7 LUTs. Clock cycle-exact.
| [https://github.com/MicroCoreLabs/Projects MCL65 Core]
|
|-
| [https://mrisc32.bitsnbites.eu/ MRISC32-A1]
| Marcus Geelnard
| {{yes}}
| [[Wishbone (computer bus)|Wishbone]], B4/pipelined
| 32-bit RISC/Vector CPU implementing the MRISC32 ISA
| [https://mrisc32.bitsnbites.eu/ MRISC32]
| VHDL
|-
| [https://github.com/stnolting/neo430 NEO430]
| Stephan Nolting
| {{yes}}
| Wishbone (Avalon, AXI4-Lite)
| 16-bit MSP430 ISA-compatible, very small size, many peripherals, highly customizable
| [https://github.com/stnolting/neo430 NEO430]
| VHDL
|-
| [[Nios embedded processor|Nios]], [[Nios II]]
| [[Altera]]
| {{no}}
| Avalon
|
| [https://web.archive.org/web/20101225092752/http://www.altera.com/products/ip/processors/nios2/ni2-index.html Altera Nios II]
| Verilog
|-
| [[OpenRISC]]
| [[OpenCores]]
| {{yes}}
| [[Wishbone (computer bus)|Wishbone]]
| 32-bit; done in ASIC, Actel, Altera, Xilinx FPGA.
| [https://openrisc.io/]
| Verilog
|-
| [[SpartanMC]]
| TU Darmstadt / TU Dresden
| {{Yes}}
| Custom ([[Advanced eXtensible Interface|AXI]] support in development)
| 18-bit ISA (GNU Binutils / GCC support in development)
| [http://www.spartanmc.de SpartanMC]
| Verilog
|-
| SYNPIC12
| Miguel Angel Ajo Pelayo
| {{yes|MIT}}
|
| PIC12F compatible, program synthesised in gates
| [http://projects.nbee.es/display/IPCORES/SYNPIC12+8bit+RISC+CPU+core nbee.es]
| VHDL
|-
| [[xr16]]
| Jan Gray
| {{no}}
| XSOC abstract bus
| 16-bit RISC CPU and SoC featured in Circuit Cellar Magazine #116-118
| [http://www.fpgacpu.org/xsoc/index.html XSOC/xr16]
| Schematic
|-
| [[YASEP (architecture)|YASEP]]
| Yann Guidon
| {{yes|AGPLv3}}
| Direct SRAM
| 16 or 32 bits, RTL in [https://web.archive.org/web/20121207045204/http://yasep.org/VHDL/ VHDL] & [http://yasep.org/#!ASM/impASM#examples/keywords.yas asm] in [[JavaScript|JS]], microcontroller subset : ready
| [http://yasep.org yasep.org] ([http://www.mozilla.com/ Firefox] required)
| VHDL
|-
| [http://zipcpu.com/about/zipcpu.html ZipCPU]
| [http://zipcpu.com/about/gisselquist-technology.html Gisselquist Technology]
| {{yes|GPLv3}}
| Wishbone, B4/pipelined
| 32-bit CPU targeted for minimal FPGA resource usage
| [http://zipcpu.com/about/zipcpu.html zipcpu.com]
| Verilog
|-
| [[ZPU (microprocessor)|ZPU]]
| Zylin AS
| {{yes}}
| [[Wishbone (computer bus)|Wishbone]]
| Stack based CPU, configurable 16/32 bit datapath, [[eCos]] support
| [http://opensource.zylin.com/zpu.htm Zylin CPU]
| VHDL
|-
|RISC5
|Niklaus Wirth| Niklaus Wirth
| {{yes}}
|Custom
|Running a complete graphical Oberon System including an editor and compiler. Software can be developed and ran on the same FPGA board.
|[http://www.projectoberon.com/ www.projectoberon.com/]
|Verilog
|}

== See also ==
* [[System on a chip|System-on-a-chip]] (SoC)
** [[Network on a chip|Network-on-a-chip]] (NoC)
* [[Reconfigurable computing]]
** [[Field-programmable gate array]] (FPGA)
* [[VHDL]]
* [[Verilog]]
** [[SystemVerilog]]
* [[Hardware acceleration]]

==References==
{{Reflist}}<!--added above External links/Sources by script-assisted edit-->

== External links ==
* [https://web.archive.org/web/20091026171102/http://1-core.com/library/digital/soft-cpu-cores/ Soft CPU Cores for FPGA]
* [https://web.archive.org/web/20070615082550/http://www.ews.uiuc.edu/~pdabrows/soft_processor_comparison.html Detailed Comparison of 12 Soft Microprocessors]
* [http://www.fpgacpu.org FPGA CPU News]
* [http://f-cpu.org Freedom CPU website]
* [http://opencores.org/projects Microprocessor cores] on Opencores.org (Expand the "Processor" tab)
* [http://www.niktech.com NikTech] 32 bit RISC Microprocessor MANIK.

{{Soft microprocessors}}
{{Programmable Logic}}
{{DEFAULTSORT:Soft Microprocessor}}
[[Category:Soft microprocessors|*]]