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May 2003

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OS/2 and Mainframes: The Linux Answer?

By Timothy Sipples© May 2003

I'm always learning something new about OS/2 Warp, and today is no exception. OS/2's history of virtual machine technologies is a little richer than even I thought. Read on for how this history might affect "Linux/2"...

It seems IBM wasn't the only vendor to use OS/2 in its mainframe product line. (Examples include the IBM P/390 and various controllers. OS/2 is used as a supervisor operating system, typically.)

Unisys did the same thing with its MicroA product line. Their A series mainframes originated with the Burroughs architecture. The MicroA system had a small A-series processor installed, and various versions of OS/2 (and occasionally a weird Unix flavor) were used to manage the system. (There were several models.) MicroA systems could run Unisys A series mainframe applications at about one four hundredth the speed of their then fastest mainframe, give or take.

Unisys (Burroughs) A series equipment was reasonably popular among banks and other financial institutions. I can only guess the MicroA systems were sort of Unisys' small branch bank servers. The MicroA's micro-mainframe processor ran an operating system called MCP (Master Control Program). Of course, OS/2 was really the master, and MCP was the slave. :-)

The MicroA systems were never certified "Y2K ready," due only in part to the fact they never upgraded to OS/2 Warp. (The first MicroAs used 16-bit OS/2 1.0, in fact, with up to 2.1 in later models.) So it's usually possible to acquire them for the cost of freight if you're so inclined.

Unisys mainframes are now sold under the ClearPath brand name. IBM's zSeries mainframes thoroughly dominate the market today, and IBM is doing a brisk business with zSeries Linux.

Nowadays mainframe operating systems can run entirely in software emulation. Developers are the main beneficiaries, since PC hardware doesn't have all the 24x7 production-grade features that businesses need and that are only found in real mainframes. And, of course, mainframe hardware is faster than software emulation. Examples for IBM mainframes include FLEX-ES and Hercules. Hercules is open source, by the way, so if anyone would like to port it... :-) The Hercules web site is here:

I should note that, with the exception of FLEX-ES, you won't get license rights to IBM's newer mainframe operating systems such as z/OS, OS/390, VSE, TPF, etc. But Hercules would be a very interesting way indeed to run genuine Linux (zSeries flavor) on eComStation and OS/2 Warp.

OK, let me repeat that. Porting Hercules to eComStation and OS/2 Warp would mean the ability to run any (legally licensed) software compatible with IBM mainframe processors, including 64-bit zSeries. And including free 64-bit mainframe Linux! My hunch is that porting Hercules would be relatively easy. So go ahead, take a look, and see what you think.

I'm quite convinced that open source virtual machine technologies are the wave of the future, and I think it's important as a community to embrace them now, both for "host" and "guest" operation.

Open source X86 emulation, by the way, is available in projects such as Bochs and Plex86.

Speaking for myself, of course, and not necessarily my employer.


   FLEX-ES -
   Hercules -
   ThinkPad with FLEX-ES -
   Bochs -
   Plex86 -

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