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The Hercules System/370, ESA/390, and z/Architecture Emulator (hercules-390.eu)
81 points by emersonrsantos 16 days ago | hide | past | web | favorite | 33 comments

The learning curve for Hercules can be pretty steep, as it drops you in to a working version of MVS 3.8j. If you are familiar with all that means, you are golden. The rest of us need some guides. Moshix has a great YouTube channel with lots of good videos. I started with his "IBM’s MVS 3.8 on Linux for newcomers - M50"[0], and I had a sample ancient COBOL program, with assembly language subprograms, running in under an hour. My main issue was the editor or shell (not sure which) locking up and not able to get out. I can kill the Linux process, but that leaves all the mounted disks in a slightly corrupted state, and doing the equivalent of fsck is beyond my skill level. I just reinstalled the Hercules package again, with a pristine set of disks, but that isn't going to help if I had a real program I was working on. Maybe there is a recovery guide for common hangups that I haven't discovered yet.

[0] https://www.youtube.com/watch?v=N6sK_BhVD8g

> The learning curve for Hercules can be pretty steep, as it drops you in to a working version of MVS 3.8j.

Hercules does not come with MVS 3.8j, that just happens to be the version of MVS that is available publicly. You can also run several other mainframe operating systems on it.

> My main issue was the editor or shell (not sure which) locking up and not able to get out.

More likely, the terminal locked up. If you try to type where there is no field to type into, you'll lock the keyboard. To reset it, press Escape, then tab to the field you want to type in.

depending on which x3270 terminal emulator you are using. There is a separate window for additional keyboard keys, eg. 'PA1' should reset your locked ISPF screen or locked cursor.

Hercules is really cool! There's even a old version of the zOS ADCD on pastebin you can download and get IPL'd in Hercules. But if you want to just muck around with a current zOS environment check out master the mainframe and grab a learning ID. Then get playing around!


Has the MTM/learning system been submitted to HN before, do you know? I'm getting kinda tired of copy-pasting the same links over and over :)

Once without traction: https://news.ycombinator.com/item?id=22783438. Submit it again.

Thank you. I can't believe I only just noticed the 'search' box at the bottom of the page...

FYI Unisys also makes available free emulators of their two mainframe environments. The ex-Burroughs MCP IMHO is a lot more interesting than the yucky IBM stuff.

Indeed, ClearPath is one of the few surviving OSes written in a (almost) memory safe system programming language, 10 years older than C.

Sadly most people don't get exposed to these kind of platforms and think that until 1973 everyone was doing Assembly only OSes and then came C out of nowhere.

I tried, but without good tutorials, it's incredibly hostile.

I can understand why Bonnie McBird named Tron's villain after it.

Her husband, Alan Kay, was at Unisys back then.

Do you happen to have a link to it?

I've been playing with MVS 3.8j on Hercules on and off for the last year and found it rather interesting. I'd love to play around with the Unisys stuff as well, since I've never used it before.

I went looking for it myself a while back:


Unfortunately, I haven't got access to a Windows machine at the moment.

There is a guy on Youtube, moshix, that does a number of videos on IBM mainframes and does quite a bit with Hercules and various OS distributions that run on it. He helped my remember some stuff from my early career. I was able to get some of my old FORTRAN code running on a MVS 3.8 setup.

I also setup a vm370 system with a few different things running on an older Raspberry PI. It was fun to think I could run the old application I maintained on a system that is about the size of the pack of cigarettes my old boss use to keep on his desk.

If you feel like a quick visit to your own mainframe, you can use this:

    docker run -it -p 3270:3270 rbanffy/vm370

That's cute that it runs on port 3270.

I thought everybody did it that way!

We could standardize on port 3277 for 12-line, 40-column uppercase displays, 3278 for monochrome with a beautiful and warm shade of green and 3279 for color ;-)

Thanks for your 3270 font by the way. It's my daily driver for terminal sessions.

Thank you for the encouragement. :-)

I put MVS 3.8J (emulated under Hercules) inside a Docker container – https://github.com/skissane/mvs38j

The idea of running a 1970s vintage operating system inside a Docker container amuses me. Old meets new. (For extra "old meets new", I should make it run under k8s.)

Most active development is happening on the SDL fork I believe:


It is easy to up (I were an Ibm system programmer for dos/vse and doing xa migrate your esa). But writing a cobol program is hard as far as I find. Hope it is better these days.

I have some old mainframe modems and online information on them are scarce (basically nothing outside of old ads). I'd like to figure out how it worked, but no idea how to get started. Are the drivers something that the OS would support built-in, or would you have to install them somehow. Would this emulator help me at all?

Do you have a model number?

It's most likely a synchronous modem meant for 4 wire leased lines, which don't really exist anymore.

Yep, the model is 3865-2. Would it be possible to create a "fake" four wire leased line? I've looked into creating fake dial up lines for DSL modems and that seems to be possible.

Should be. The 4 wire connection is the round one on the back. You would need to crossover the tx and rx pairs between the modems.

The other port is standard rs232.

Cool, as far as protocol / communication standards go am I looking at one of the V.x standards?

I've always associated the "Hercules" name with the mono-monitor from the past :)

I had what I think may have been a CGA and EGA emulator, so even though I was in monochrome, we could still run high resolution graphics with a little grayscale. Very nice. I wonder if DOSBox can do that...

Jay Maynard (tron guy) is a really talented guy!https://www.youtube.com/watch?v=t9dutFhebw4

That was very painful to watch. I feel like he never even started.

People have such short attention spans and the judges kept making him start over repeatedly... and when they started booing I genuinely felt for the guy.. Props to the guy for keeping clear, that would have destroyed my spirit.

Any chance to get MTS running?

I remember exploring MTS back in the day, UBC was running it on some kind of machine in the mid-1970s.

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