Re: New Vax - future directions :-)

[Jason Thorpe <thorpej%me.com@localhost>]

> On Jul 7, 2021, at 8:41 AM, Johnny Billquist <bqt%update.uu.se@localhost> wrote:
> 
> This might be extremely hard, since it's a feature that comes from the design of the PDP-11 MMU. The VAX MMU is very different, and don't allow this. (Allow might be the wrong word here - it's just not possible.)
> (Anyone talked about execute-only protection of memory... The PDP-11 have it. :-) )

During the brainstorming of how to do a VAX-64 VM, I did mention that a split ITLB / DTLB would be useful for various reasons (and how it could be made "classical VAX-32" compatible), and so emulating a split I/D address space might be somewhat feasible on such a system.

-- thorpej