I just stumbled across this,

http://www.hercules-390.org/

This is an emulator for the old S/370 (and other) IBM mainframes that runs on a PC under Windows and Linux (may be a Mac version in there as well). Turns out that some of the older IBM mainframe OSes are in the public domain now (I didn't know that at all), so you can have a ball running your own little virtual mainframe. The FAQs go into detail on just what is actually legal to run under Hercules.

It will be as much fun for me to compile and build the sucker from source as it will be to run it. It's been a long time since I messed around with a mainframe system -- goes way to my college days.

The amazing thing is that this PC emulator will be faster than some of the original 70s era hardware. Moore's Law in action.

-Richard

Yep; We've got a VMS emulator. As the VAXs are getting un-fixable, we are moving some of our applications to virtual VAXs. They work great.

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Can I program them on virtual punchcards and mount virtual tapes? And can I get my output on virtual green and white stripped paper?

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Wow. My first graphics card was a Hercules. When everyone else was doing eight colors, it could do sixteen! Sixteen colors!

Can you believe it??!!!

Of course, it may not be the same company that did the emulator...

I wish Microsoft had kept backwards compatability with DOS. I used to have close to a hundred little utilities I'd written from scratch. Most of them died with NT 4.0.

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Whoever says "perception is reality" is daft. It's merely an abstraction, and often not a very good one.

Hercules is the name of the emulator, not a company and it's open source and free. The only question is the status of whatever OS and app software you'd run under it.

32-bit XP and Vista still have NTVDM which runs DOS and old Win-16 programs. I still run a lot of DOS programs under it and most of them run fine. The only problem is programs that try to mess around with hardware that NTVDM doesn't virtualize (it virtualizes the display, COM ports, and other common things -- most all DOS programs wrote directly to video memory so it would be worthless if you didn't virtualize that).

The Windows DDK still includes documentation on building NT .VDD drivers (very different from Win9x VxDs) which plug into NTVDM and allow you to trap and virtualize any behavior of your DOS programs you like. Well, it was still documented in the Win2K3 SP1 DDK -- don't know about the latest Vista and Win2K8 kits.

The x64 versions of XP and Vista dropped NTVDM because the x64 CPUs dropped V86 mode under the 32-bit compatibility mode of 64-bit native mode. It's still there in 32-bit mode, just not available when running in full 64-bit mode. IIRC, it would be possible to run 16-bit protected mode programs under that 32-bit compability mode (the 16 vs 32 bit segment selectors still work as normal), but the Win3.x environment depended on DOS being underneath. Without V86 mode, you can't run a virtual DOS underneath.

However, Virtual PC, VMWare and similiar (such as DOS Box) are the solution there, and since it provides a full virtual machine, emulating basic PC hardware, many programs that mess with the hardware in various ways incompatible with NTVDM will run. I run a DOS 6.22 virtual machine with Windows for Workgroups 3.11 on top just for fun under the 64-bit version of Virtual PC under the x64 version of XP.

-Richard

IBM's OS/2 (now distributed as eComStation by Serenity Systems) has kept its compatibility with DOS all along. I still run a few Windows 92 (er, Windows 3.1) programs with it.

There is also a provision for running DOS from floppy drive A: under OS/2 for particularly fussy programs requiring particular drivers. One interesting use that I made of this feature recently was to run MikeOS 1.0 from a floppy in such a box. MikeOS is a very small and limited real-mode operating system that is small enough to serve as a teaching example.

eComStation is now up to versions 1.2 (current retail) and 2.0-RC5 (soon to be released as the next retail version). A little pricey, but worth it if Microsoft means nothing to you.

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Ah yes. OS/2 2.x - 4.x run well under Virtual PC and I have virtual machines set up running Warp 3 and 4. Playing around, I re-discovered the "DOS from Drive A:" option, which loads a real copy of DOS (or as you mention, any compatible 16-bit real mode OS) into a virtual real mode machine which runs under V86 mode and is virtualized at the BIOS level.

So I did that to play around (used MS-DOS 3.3, IIRC), and thought it was funny. I was running a virtual machine under a virtual machine (and you carry that to more levels sometimes).

Unfortunately, OS/2 1.x will not run under Virtual PC (I don't know about VMWare or some of the others). Virtual PC doesn't emulate some of the old 286 "black magic" instructions (some of that was infamously undocumented by Intel, and only the major Intel allowed in the inner circle knew about it) required for it to run. It does real mode and 32-bit mode fine, just doesn't bother with the 286-only level.


-Richard

Wow.... I could get out all my old COBOL and assembler programs from my ancient college days..

;-)

Yes, I've seen things like that. I still have access to the real thing (modern IBM mainframes), but am happy when I don't need to use it, so I don't think I'll run to try this on a home computer.

Back in '89, I went on a tour of a huge data center. One thing I remember specifically was a room that reminded me of the warehouse scene at the end of Raiders of the Lost Ark. Row upon row of dishwasher sized hard drive units filled the somewhat darkened room. The guide smiled with pride as he told us the capacity of those drives: Two gigabytes each, and with a total of about 300 units, they could store an amazing 600 gigabytes in that room.

Today, I have over 1,400 gigabytes on my home computer.

Where the IBM mainframe excels is dealing with large amounts of data. CPU speed isn't too astonishing, and forget serious graphics, but if you have a lot of data to be accessed by a lot of people, it does a good job.

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I'm pretty sure that I've got textbooks at home on JCL and CICS. I learned COBOL in college on an IBM mainframe. I'll never forget how the professor (who had been a Kingfisher pilot in WWII) called variables "buckets"

Good times, good times.

Well, the source code is 11.9MB in ~470 files. The whole thing is written in C (not C++, mind you, plain old C, right up my alley). The specifically avoided dropping down to assembler to keep the thing as cross-platform compatible as possible.

I'm going to have fun turning Intel's highly optimizing compiler loose on this thing.....

Most of my dinky little programs aren't enough for it to get warmed up.


-Richard

Well, shoot, that wasn't too much fun. The whole thing compiled under VC 2005 in 5:08 minutes (and added another 90MB of binaries). They're Linux/UNIX geeks (of course) so they use makefiles, which means it will take a bit of tweaking to use Intel's compiler. But not much.


-Richard

Curious. I assume you mean PC based VAX emulators. If they require windows, it seems a little weird to take one of the more robust operating systems, VMS, and run it under one of the most vulnerable.

Speaking of VMS, I assume the virtual vax machine runs VMS as well. For us, we are replacing our vax machines not due to hardware (which is a problem at times) but more due to VMS being a dead-end. For example we can't upgrade Oracle on the vax machines because the new versions won't run on VMS.

Yes... VAX not Alpha.
Well; when you have the core software of a billion dollar business running on VAXs, it's kind of hard to move everything to a new platform. Until we are up and running on new software, we are stuck with it for a while.
All our ancillary systems have migrated to other platforms though.

We have a joke around here that when the big bomb hits, the only things that will survive are cockroaches and our VAX systems.

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I wonder if nano-tube rope memory exists

I always knew I was good for something.

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Wow, Publius! I had no idea you were so well-versed in the inner workings of computers!

I knew that from NT on the DOS was VM'd. In my opinion, 95/98/ME tanked a lot because it tried to be two things at once, rather than being a good platform with an emulator for the earlier programs.

Thanks for refreshing my memory... I never installed the non-volatile stuff!

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I am Mugs, of the Alien clan of Usa, Nordamerica, a Terran, of Sol. Human.

Whoever says "perception is reality" is daft. It's merely an abstraction, and often not a very good one.