Any word on the Multics revival front?

Charles Anthony at
Sat Mar 12 12:49:56 CST 2016

On Sat, Mar 12, 2016 at 10:37 AM, Kevin Monceaux <Kevin at>

> On Fri, Mar 11, 2016 at 08:51:28PM -0800, Zane Healy wrote:
> > What I’d like to know is if any copies of GCOS-8 exist in the wild.
> > That’s what I’d personally really like to boot on the emulator.
> I would too.  I've always been curious about Honeywell OSes.  Well, I'm
> curious about any mainframe OSes I've never had contact with, which is most
> of them.  I currently work as an IBM z/OS operator, so I'm mostly familiar
> with IBM OSes.  I went to college briefly at Lamar University in Beaumont,
> TX in '88-'89.  Sadly I dropped out during my second semester.  The
> computer
> science department had an overworked VAX 11/750.  I worked as a volunteer
> operator on that system.  I heard the engineering department had a
> Honeywell
> mainframe.  There was one Honeywell terminal room in the computer science
> building that was used by a FORTRAN programming class.  The doorway to that
> terminal room was the closest I ever got to the campus's Honeywell.  I
> don't
> know what model it was, or what OS it ran.  I still regret not finding out
> more about it while I was there.  And that has made me especially curious
> about Honeywell OSes.
Multics includes a GCOS (6 I think) emulator which allows some GCOS
programs to run under Multics. (The GCOS emulator copies the GCOS program
to a segment, and executes the segment in BAR mode with an offset of 0; the
GCOS application does OS calls with the MME (Master Mode Entry)
instruction. The GCOS emulator intercepts the MME calls with Multics
exception handler, deciphers what the call wants, does it, and continues
the GCOS program.

Several of the GCOS applications provided as part of the Multics
distribution work; such as the DN355 cross assembler. (Let's see: running a
cross assembler under a GCOS simulator running under Multics, which is
running on emulated hardware. </scratch head>).

There is a also the GCOS TSS subsystem which is an interactive programming
environment supporting several languages (Multics includes the BASIC and
FORTRAN runtimes). Sadly, there remain some emulator bugs that are causing
some failures under TSS; and lacking the source code for TSS, it is proving
to be an intractable issue.

-- Charles

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