Re: NVAX page format (Was: NetBSD/vax 512MB support)

[David Brownlee <abs%absd.org@localhost>]

On Wed, 31 May 2023 at 13:14, Johnny Billquist <bqt%softjar.se@localhost> wrote:
>
> On 2023-05-31 14:59, David Brownlee wrote:
> > On Tue, 30 May 2023 at 13:04, Johnny Billquist <bqt%softjar.se@localhost> wrote:
> >>
> >> On 2023-05-30 13:59, David Brownlee wrote:
> >>>
> >>> That's fine, the changes are all in (and will remain in) trunk (unless
> >>> someone comes up with a further way to have NetBSD support VAXen with
> >>> 2GB of mapped memory :-p)
> >>
> >> I don't think we support the newer NVAX page table format, so that would
> >> be quite some work... :-)
> >
> > Sounds like an interesting project (and a nice complement to the gcc
> > improvements allowing native compiling again). I Assume simh emulates
> > the NVAX page table format?
>
> Pretty sure simh does *not* emulates the new page table format
> introduced in the NVAX. The NVAX can also run with the old page table
> format, so there is no actual need for the new format unless you want to
> have more than 512M of physical memory.
>
> But simh actually only emulates a rather narrow subset of VAXen, and
> none based on the NVAX as far as I can remember.

Ahh.. it's just the KA49 in the 4000/90 which was NVAX, not the
earlier M60. My mistake.
That makes it more challenging, though finding someone interested in
implementin in simh could make a good collaborating project...

> > Anyone up for the challenge? :-p
>
> Start with doing it in simh then. You could maybe get away with doing
> something like the VAXstation 4000 series for a NVAX based machine, but
> I think the only VAXen that actually could have more than 512M was the
> 7000, which means you'll need XMI and VAXBI implemented, along with
> whatever controllers (disk and ethernet at least) to even boot.
> Then you can test that with VMS, before we start playing with NetBSD...
>
> It's going to be quite some work...

Definitely. Something to leave on a wishlist until the right
intersection of person and time arrive...

Thanks

David