Re: Removing SunOS/68k compatibility before 8.0

Swift Griggs <[email protected]> writes:

>> 2. Who knows what exactly has to change for extending the virtual
>> address space?
>
> Since the VAS is independent of the PAS, shouldn't simply increasing
> the size of the page table that tracks the virtual memory increase
> it's upper limit? I'm guessing for some reason it's not that
> easy.

Indeed. The Sun-3 MMU was custom made by Sun and honors only 28 bits of
VA from a given address (the "context" is global). That could explain
the existence of a historical limit for SunOS emulated processes.

See pages 7 and 8 of http://www.bitsavers.org/pdf/sun/sun3/Sun-3_Architecture_Manual_Ver_1.0_Jan85.pdf

It certainly means, however, that a new higher limit couldn't be handled
by lower-end Sun-3's which NetBSD has support for (sys/arch/sun3/sun3).

Later models based on 68030's used the integrated Motorola MMU which is
32-bit (sun3x).

It doesn't mean NetBSD couldn't have different limits for processes
under different emulations and/or different limits on different m68k
ports.

Regards,
 Aymeric