[Info-vax] VMS port to x86

[John Wallace]

On May 31, 9:28 pm, JKB <j... at koenigsberg.invalid> wrote:
> Le 31 May 2012 09:35:17 -0500,
> Bob Koehler <koeh... at eisner.nospam.encompasserve.org> écrivait :
>
> > In article <slrnjse7if.ul.... at rayleigh.systella.fr>, JKB <j... at koenigsberg.invalid> writes:
>
> >>        That's why VMS should not be ported on x86, but on top of a real
> >>        microkernel. L4 is a good candidate as it is compact and simple. If
> >>        you want to port your OS on another processor, you only has to port
> >>        microkernel (and toolchain).
>
> >    Port VMS to the hardware and you get the behaviour of VMS.
>
> >    Rewrite the VMS kernel and APIs to sit on top of a micro-kernel and you
> >    get some other behaviour, limitted by what the micro-kernel can do.
>
> >    There are a great many applications that won't care.  And some that
> >    will.
>
>         And why ?
>
> --
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Because most user mode applications mostly don't (or at least
shouldn't) care about the exact behaviours of the underlying OS? Such
user mode stuff probably already works fine in one of the various
readily available VAX or Alpha emulators, subject to the usual
commercial considerations, so a DIY VMS is not necessarily of major
interest. Not necessarily a bad idea, but not necessarily attractive
to IT departments and end users who just want a way to run routine VMS
applications.

On the other hand, VMS would happily let you run complex kernel-mode
and/or real-time stuff on the same box that was supporting interactive
and batch users. It may not always have been a bright idea to do that,
but it usually worked. Sometimes these things came to depend on
behaviours that weren't formally documented but were predictable and
reliable; sometimes that kind of dependency happened even without the
interactive and batch users.

If micro[kernel]VMS doesn't demonstrably have those same reliable and
predictable behaviours, it is probably of no interest to this class of
application. There may not be lots of people in this class, but if the
rest of the users are happy with an emulator...