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

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.

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...


Johnny Billquist                  || "I'm on a bus
                                  ||  on a psychedelic trip
email: bqt%softjar.se@localhost             ||  Reading murder books
pdp is alive!                     ||  tryin' to stay hip" - B. Idol

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