I am looking for impressions, memoirs, articles, guidelines - everything that is possible about the unusual direction of software migration. I am interested in non-Unix related code, and preferably highly optimized code - perhaps even assembly language, and large enough software products - if this ever happened. It would be especially interesting if there was information about porting from Atari ST / TOS / GEM (or at least Apple Macintosh) to DEC MicroVAX / VAX/VMS / DECWindow something with an advanced interface and advanced work with I/O in real time.

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    I would be extremely surprised if anything was every ported in this direction ... but one never knows.
    – dirkt
    Commented Feb 5, 2021 at 11:47
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    I suspect that anything outside of "pure compute" would be hard to port, due to the probably quite huge difference in syscalls, window systems, and all other "not pure compute" bits.
    – Vatine
    Commented Feb 5, 2021 at 12:20
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    Yes, I did this a few times for real-time applications. When I get a spare half hour, I'll write you a proper answer.
    – Chenmunka
    Commented Feb 5, 2021 at 13:31
  • Sounds like a very special and unusual use case. After all, at a time the Atari way a thing (1985-90) and considering that any such application would have nesd some time to develop we reach a time were VAX class machines were already on the way out. Having said that, I know of medical applications developed by students on Atari that have been ported to DEC systems operated by their institutes. But only few, more often than not the Atari was simply integrated into the existing landscape.
    – Raffzahn
    Commented Feb 5, 2021 at 20:55
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    But why would you port something like a sound/music application that works perfectly fine on a cheaper computer to a more expensive system? Just buy a few dozen Ataris or more instead of the one VAX ... and no costs for porting.
    – dirkt
    Commented Feb 6, 2021 at 7:57

1 Answer 1


I can give you an anecotal answer. I did this a few times.

I suspect that porting in this direction would have been unusual. We only did it where the customer insisted on the use of Vax hardware.

The company I worked for for many years specialised in real-time process control and communications handlers. We made our own range of controllers, based on the 68k processors but would contract on anything.

A large library of handlers for various industry-standard protocols over dual-redundant communication paths, dual-processor routines with both hot standby and 2oo2 for fault tolerance had been built up over years and had a proven track record. These libraries had a core of 68k Assembly Language and a C wrapper.

A bulk material handling application for the Kwangyang steelworks in South Korea was specified to run on a dual hot-standby MicroVax configuration. Commissioned 1987.

A development of this, on a Vax-FT was commissioned in 1992 to control the signalling of Seoul Subway Line 5. Here we used both halves of the FT and our own library.

Another dual MicroVax system was installed in a British Steel Tinplate works in Ebbw Vale, Wales in the early 90s. This had a much more complex communication configuration.

Porting involved adapting the code to use the VMS interprocess communication techniques, mutex, event flags etc, keeping our own real-time handlers. This way we kept our own communications failover techniques and had tight control on the fault tolerance.

Porting in this manner was seen as a good idea at the time. The belief being that it gave the best chance of achieving the project deadlines.

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    It's interesting that your first VAX customer was willing to take the risk of porting the software just so they could keep the hardware the same! Commented Feb 6, 2021 at 15:04
  • Did you have some way to mechanically translate from 68000 assembly to VAX assembly? I imagine that would have been quite hard to get right. You might have had to do some fancy register reallocation. Commented Feb 6, 2021 at 17:13
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    @snips-n-snails My understanding was that Vax hardware was made under licence in Korea, thus saving import duties. But I wasn't involved in the contract negotiations.
    – Chenmunka
    Commented Feb 6, 2021 at 18:29
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    @OmarL: No, all by hand, but in those days, that is what we did - write in assembler of whichever processor was in front of us. It wasn't that uncommon.
    – Chenmunka
    Commented Feb 6, 2021 at 18:30

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