OS-9/68k Control Coprocessor module

Charles Dickman chd at chdickman.com
Wed Jul 29 18:08:17 CDT 2020

I came across an Allen-Bradley 1771-DMC4 Control Coprocessor. If you are
familiar with AB PLC's, it is a 1771-IO chassis module that could be a
"sidecar" for a PLC5 PLC or a standalone module.

It runs some version of OS-9/68k on a 68340 processor. It has 4MB static
ram and a 10MB ethernet AUI connector. I hooked up a terminal and can get
to an OS-9 prompt. It has by default a 64k RAM disk that is empty. The best
I can gather is that there was an external IDE (AB 1771-PCB PCbridge) that
was used to create programs that were loaded onto the RAM disk. Once
configured it would run standalone.

Microware is still around in some form so OS-9 is not completely dead and I
did find some references to a Microware product called PBbridge. It would
be interesting to experiment with.

I am curious if anyone has any experience with this hardware, with the IDE
or OS-9/68k in general. I've never seen much discussion of OS-9/68k on

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