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Hercules is OSI Certified Open Source Software

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

SDL Hercules 4.x Hyperion

This is the official web page for the SDL 4.x version of the hercules-390 mainframe emulator, code named "Hyperion".

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.

This version of Hercules is the SDL version of the Hercules emulator containing fixes to address bugs that may or may not still exist in the original 3.x and/or 4.0 versions of Hercules, or to add new features and functionality above and beyond what exists in the original versions. SDL Hercules 4.x Hyperion is consider to be the most current up to date version of the Hercules emulator in existence at the time this writing.

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.

Please Note that this version of Hercules is only called the "SDL" version in order to distinguish it from any other versions of Hercules that may be out there, and not for any other reason. This version of Hercules was neither created by, nor is owned by, nor maintained or supported by Software Development Laboratories. Hercules it not the work of any one person. It was created by many very smart and talented individuals over the course of many years. For a list of just some of these many very talented people, please refer to question 6.01 of our FAQ.


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

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

To find out more about this particular version of SDL Hercules 4.x Hyperion, follow these links:

What's New, Release Notes, etc:

  • What's new in this version    (List of major changes)
  • Release notes                     (Important information about this version)
  • Issue Tracker                        (Please report your bugs here)
  • Support Forum                      (Where to ask questions or get help)
  • README                              (Miscellaneous supplemental documentation)
  • Community Wiki                    (Hercules is only as good as you help make it)

Web documentation:

The below web pages are, at this time, the only accurate source of documentation for SDL Hercules 4.x Hyperion.

Source code and binaries:

GitHub source code repository:

The complete source code to the current bleeding edge development version of SDL Hercules Hyperion is available via anonymous access to our git source code repository.

Please note that, as a bleeding edge development repository, it may contain faults (bugs) which may or may not be fixed at an unspecified later date, and might contain experimental code that may not appear in future releases.

Build instructions are contained in the source files BUILDING and INSTALL (for Unix) or README.WIN64 (for Windows). Fish also has a "Hercules Windows Build Instructions" web page on his SoftDevLabs web site.

SDL Hercules Hyperion     (https://github.com/sdl-hercules-390/hyperion)

This repository is the official SDL version of Hercules 4.x Hyperion containing fixes for bugs that may or may not still exist in other versions of Hercules. It also contains support for QDIO/OSA, MPCPTP6 networking interfaces, a redesigned I/O subsystem and many other advanced features above and beyond the original version of Hercules.

Minimum supported host platforms:

  • Windows

    The current minimum supported Windows platform is Windows Vista. Anyone still running a version of Windows older than Windows Vista is strongly encouraged to upgrade to Windows Vista or greater with Windows 7 being the preferred choice.

  • Non-Windows


If you have any questions or comments  please consider joining the hercules-390 discussion group at groups.io.

Bug reports for SDL Hercules Hyperion (together with your diagnosis of the fault, please!) should be entered into our Github issue tracker (preferred):

or alternatively via message to our discussion group: If your question or problem is specific to a partuclar mainframe operating system product, you might consider joining one of our more focused support groups:

Other Hercules-related sites

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.