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Hercules is OSI Certified Open Source Software

The Hercules System/370, ESA/390, and z/Architecture Emulator

Hercules is an open source software implementation of the mainframe System/370 and ESA/390 architectures, in addition to the latest 64-bit z/Architecture. Hercules runs under Linux, Windows, Solaris, FreeBSD, and Mac OS X.

Hercules is OSI Certified Open Source Software licensed under the terms of the Q Public Licence.

Hercules was created by Roger Bowler. Jay Maynard (“the Tron Guy”) was the maintainer from 2000 to 2012. Jan Jaeger designed and implemented many of the advanced features of Hercules, including dynamic reconfiguration, integrated console, interpretive execution and z/Architecture support. A dedicated crew of programmers is constantly at work implementing new features and fixing bugs.

To find out more about Hercules, follow these links:

Web documentation:

PDF manuals:

To download the current release version, use the following links:

  • Source code:

  • Windows binaries:

    • hercules-3.13-w32.msi: Windows 32-bit Installer package
    • hercules-3.13-w32.zip: 32-bit binaries only archive
    • hercules-3.13-w64.msi: Windows 64-bit Installer package
    • hercules-3.13-w64.zip: 64-bit binaries only archive

      Note: Installing the .msi Windows Installer package ensures the required Microsoft Runtime components are installed and also provides convenience shortcuts in the programs menu. If the required components are already present and the shortcuts are not needed on the target system, the self-extracting or .zip archive may be used instead.

What people are saying about Hercules

“ Never in my wildest dreams did I expect to see MVS running on a machine that I personally own. Hercules is a marvelous tool. My thanks to you all for a job very well done. ”
— Reed H. Petty

“ I do miss my mainframe a lot, and playing with Herc sure brings back memories. Just seeing the IBM message prefixes, and responding to console messages again was a wonderful bit of nostalgia! ”
— Bob Brown

“ I have installed your absolutely fantastic /390 emulator. You won't believe what I felt when I saw the prompt. Congratulations, this is a terrific software. I really have not had such a fascinating and interesting time on my PC lately. ”
— IBM Large Systems Specialist

“ Such simulators have been available for a long time. One of the most complete (up to modern 64-bit z/Architecture) is hercules. ”
— Michel Hack, IBM Thomas J. Watson Research Center

“ An apparently excellent emulator that allows those open source developers with an "itch to scratch", to come to the S/390 table and contribute. ”
— Mike MacIsaac, IBM

“ BTW grab a copy of Hercules and you can test it at home. It's a very good S/390 and zSeries (S/390 64bit) emulator.. ”
— Alan Cox

“ It works even better than I imagined. Hercules is a fine piece of software! ”
— Dave Sienkiewicz

“ Hercules is a systems programmer's dream come true. ”
— René Vincent Jansen

“ Aside from the electric trains my parents got me in 1953, this is the best toy I've ever been given, bar none.”
— Jeffrey Broido

“ Congratulations to you and your team on a fine piece of work! ”
— Rich Smrcina

“ Congratulations on a magnificent achievement! ”
— Mike Ross

“ For anyone thinking running Hercules is too much trouble or too hard or whatever, I came home from work one day and my 13 year old 8th grade son had MVS running under VM under Hercules on Linux. He had gotten all the information about how to do this from the Internet. When he complained about MVS console configuration and figuring out how to get it to work with VM, I knew he had felt all the pain he ever needed to feel about mainframes. ”
— Scott Ledbetter, StorageTek

“ I am running a fully graphical Centos z/Linux environment on my desktop. The Hercules emulator is an amazing feat of engineering. I just wanted to send my compliments to the team for an excellent job! Thanks much for making this product part of the open-source community! ”
— Roby Gamboa

“ I have DOS and DOS/VS running on Hercules with some demo applications, both batch and on-line. It does bring back some good memories. My compliments go to the Hercules team. Thank you. ”
— Bill Carlborg

“ This is stunning piece of work. To say that I am blown away is an understatement. I have a mainframe on my notebook!!!!!! P.S. Now if I can just remember my JCL ”
— Roger Tunnicliffe

Read Hesh Wiener's Technology News article about Hercules at http://www.tech-news.com/another/ap200601b.html

Read Moshe Bar's BYTE.com article about Hercules at http://web.archive.org/web/20010712143133/http://www.byte.com/documents/s=429/BYT20000801S0002/

For eighteen months, the IBM Redbook SG24-4987 Linux for S/390 at http://www.redbooks.ibm.com/abstracts/sg244987.html contained a chapter written by Richard Higson describing how to run Linux/390 under Hercules. Then suddenly, all mention of Hercules was mysteriously removed from the online edition of the book! Read the story of the disappearing Redbook chapter at http://www2.marist.edu/htbin/wlvtype?LINUX-VM.25658

View the foils from Jay Maynard's presentation given at SHARE Session 2880 in San Francisco on 20 August 2002 as a PDF file (815K) from http://linuxvm.org/Present/SHARE99/S2880JMa.pdf

The source code repository

The complete source code and development history for Hercules is also available via anonymous access from these git repositories:


The spinhawk repository is used to build the 3.xx series of “gold” releases. The intent of the 3.xx release stream is to provide regular production-quality releases fully compatible with version 3.07, containing additional architectural features and bug fixes, as well as selected enhancements from the developer sandbox.


The hyperion repository is used by a group of developers as a cutting-edge developer sandbox. It is currently designated as version 4.00. This repository evolved from Hercules version 3.07 enriched by a series of user interface changes and usability enhancements produced during the TurboHercules period. It also contains experimental support for the QDIO and MPCPTP6 networking interfaces and a redesigned I/O subsystem.

Please note that the development repositories may contain faults which may be fixed at an unspecified later date, as well as experimental code which might not appear in any future production release.

Build instructions are contained in the source files INSTALL (for Unix) or README.WIN32 or README.WIN64 (for Windows).

Other Hercules-related sites

If you have any questions or comments  please consider joining the hercules-390 discussion group at http://groups.yahoo.com/group/hercules-390.

Bug reports for the current release (together with your diagnosis of the fault, please) may be posted at the hercules-390 discussion group. Problems with the developer sandbox version should be entered into the Hyperion issue tracker at https://github.com/hercules-390/hyperion/issues.

IBM, System/370, ESA/390, and z/Architecture are trademarks or registered trademarks of IBM Corporation. Other product names mentioned here are trademarks of other companies.

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