Re: MMU questions?

[Konrad Kokoszkiewicz <draco@mi.com.pl>]

> Can the MMu work in both ways, Memory protection ON AND virtual
> memory?

Yes. But get a 68030 manual and read the section entitled "Memory
management unit". Then you'll understand why so few people are actually
able to program the MMU :-)

The other pain is that 68040 and 68060 have the MMU slightly different.

> If so, why can't outside work with memory protection? coz it might
> just check for the simple cookie MMU only? could it better check or
> just that it is plain impossible ? (combining vmem and mem protection)

I think OUTSIDE wasn't designed to work on systems with memory protection.
Besides, OUTSIDE is a separate TSR and I think it might conflict with the
MiNT memory protection module. The best way would be if one program (MiNT)
could manage the memory.

> 2) Is the Vmem (on Falcon for example or TT without TTram) seen as
> TTram? or ALT RAM? 

It is seen as Alternate RAM. The TT RAM aka Fast RAM is alternate RAM as
well. I.e. the VM is seen as TT RAM expansion.

That is: the physical TT RAM is used as VM buffer (sort of a cache). I.e.
it is normal TT RAM, but eventually with remapped addresses. Swapping
occurs when you try to access memory pages, those are not in this buffer.
I.e. the system writes some of this area to the disk, then fills this
place with recently requested pages.

> hence do you have 3 types of RAM on TTram computer equiped?

No, only 2.
 
> like, is it possible to have a TT with 4 of STram, 8 meg of TTram and
> 10 meg of vmem?

Yes, this time your Alternate RAM will be 18 megs (8 TT + 10 VM).

> If yes, what tool shows that correctly?

None afaik. Any need?

> 3) what is the correct pointer containing the MAX TTRAM (physical)?
> and MAX Vmem?

_ramtop should contain the highest alt ram address ($05a8).

--
Konrad M.Kokoszkiewicz
|mail: draco@mi.com.pl                  | Atari Falcon030/TT030/65XE |
|http://www.orient.uw.edu.pl/~conradus/ | ** FreeMiNT development ** |

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