Re: NetBSD in SIMH vax with 512 MB RAM

[Mouse <mouse%Rodents-Montreal.ORG@localhost>]

> The 1GB limit is because of the layout of the registers for the
> memory mapping.  [21 bits for the PFN in a PTE]

> This got an update on the NVAX, where a different format PTE was
> defined, in which you have 25 bits for the address.  [...]

> As for the division between memory and I/O space, I guess it could
> have been done differently on different implementations, but the
> complexity it would have implied in software if that had been done
> was probably not something DEC wanted.  So in all machines I've ever
> looked at, the I/O space starts at 512M.  Physical memory is always
> below that.

What happens for machines that have more than 512M of physical memory
(like that 7000 at LSSM)?  It can't _all_ be below the 512M point!

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