[Info-vax] Creating an open source version of VMS, was: Re: OpenVMS Hobbyist Notification

[Arne Vajhøj]

On 3/10/2020 9:21 AM, Simon Clubley wrote:
 > There are a number of possibilities here, if you focus on application
 > level source code compatibility and break compatibility at a lower level
 > instead, in which you could produce something which runs a good number of
 > existing applications but which has a _much_ cleaner and more functional
 > operating system underneath.

On 3/10/2020 3:05 PM, Simon Clubley wrote:
> I'm familiar with FreeVMS. One major mistake it made was trying to
> emulate the existing VMS design in great detail at a far lower level
> than it should have done.
> 
> For example, it decided to keep supervisor mode and tried to emulate
> the required additional hardware level by other means within its design.

> The above is a good example of the kind of thing I am talking about.
> 
> The application program would still have the same calls to interact with
> a modern DCL in its source code but the implementation is completely
> different, and the differences are hidden from the application source code.
> 
> Other things I would get rid of would include any support for Macro-32.
> 
> No-one writes normal applications in assembly language any more and
> modern compiler capabilities have made even the speed critical parts
> of programs less likely to need assembly language. Even when assembly
> language is required for speed in normal applications, you are going
> to be using the native assembly language anyway instead of Macro-32.
> 
> There could also be a strong emphasis on a truly modular kernel design,
> so that XQP (for example) would be discarded and replaced with a modular
> plug-in architecture.
> 
> My point is that you can have a vastly improved design that looks nothing
> like current VMS internally and yet still manages to present a strongly
> compatible VMS environment to normal VMS application source code written
> in C or other higher level languages.

I see very little interest in such an OS.

It would look like VMS, but because of all the
"improvements" then a lot of existing VMS stuff would
not run as expected.

It makes sense to have VMS be VMS.

It makes sense to create something new.

But something that is mostly but not fully
VMS I do not see any demand for.

It will be like demand for an almost C
compiler.

Arne