[Info-vax] VAX VMS going forward

[Simon Clubley]

On 2020-07-23, Stephen Hoffman <seaohveh at hoffmanlabs.invalid> wrote:
> On 2020-07-23 17:38:33 +0000, Simon Clubley said:
>> P1 space would also be right in the way of a flat 64-bit addressing 
>> mode so all the code which uses P1 space would have to be rewritten to 
>> support flat 64-bit addresses because P1 space would have to be moved 
>> well out of the way.
>
> P0 and P1 space and S0 and S1 space are for VAX compatibility within 
> apps and app source code.
>

P1 space is a little more than that. :-)

It's where DCL and the associated data structures live.

How much work would be involved in moving what is currently in P1 space to
somewhere up the 64-bit memory map to just below where the kernel is mapped ?

For one example, how much of the P1 code and data structures are still
32-bit only ?

That would mean as well that you would have P1 data cells with different
locations on the system depending on whether you are running in 32-bit
or 64-bit mode.

There's also the question of whether flat 64-bit addresses are a process
level attribute or an image level attribute. Think about what that means
for P1 space as well as for mixing 32-bit and 64-bit applications in the
same process space.

Simon.

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