[Info-vax] relaunch or legacy

[Simon Clubley]

On 2022-01-28, John Dallman <jgd at cix.co.uk> wrote:
>
> I mentioned the idea of emulating Alpha and IPF yesterday. Emulating
> 64-bit VMS on VMS is rather easier than emulating it on a non-VMS
> operating system. The x86 VMS has, I think, all the system calls of Alpha
> and IPF versions, and thanks to the DEC calling standard, they're called
> in the same way. 
>
> So reviving the free and open-source IPF emulator I posted a link to
> today, porting it to x86 VMS, and equipping it with a system call
> translation facility would seem to be a route to running IPF VMS
> applications on x86 VMS. 
>

A system call translator might not be enough for VMS because, unlike Linux,
there are VMS applications that decide to directly look at data cells in
the process space instead of getting the data via system services.

There may be other issues due to the persistent process nature of VMS,
instead of the "create a process to run a single program and then discard
the process" nature of Linux. You wouldn't just be running a standalone
user application, but would also have to provide access to things like
DCL services via sys$cli() support.

> That gives a transition route to running on x86 for IPF customers who
> can't or won't port their applications, and gives intermediaries
> something to provide expertise on. This will require a fair amount of
> open-source software development work, but that will benefit everyone
> involved, and probably prompt improvements to x86 VMS development tools. 
>

I've had a quick look at the emulator you posted elsewhere and it appears
to be another Ski. It's not the basis for a full system emulator but with
enough effort, you _may_ be able to replace the Linux system call stuff
with a VMS system services interface.

Whether that's enough for VMS applications in general is a very open
question. For example, in addition to the above issues, are there any
implications when using RMS in this setup ?

Simon.

-- 
Simon Clubley, clubley at remove_me.eisner.decus.org-Earth.UFP
Walking destinations on a map are further away than they appear.