Re: [MiNT] CT60 and memory protection

[Xavier Joubert <Xavier-Joubert@defontaine.com>]

Hello !

Thomas Binder a écrit:
> Sorry, but why is it that big? On my Milan (with 80 Megabytes of RAM),
> the MMU tree installed by TOS just needs a few kilobytes, as it uses
> "invalid" upper level pointers for areas where there isn't any memory at
> all and accesses would trigger an access fault anyway. Or to phrase it
> differently, it only uses page level descriptors for areas where there
> is (partly) physical RAM, ROM or I/O registers. And it uses indirect
> page level descriptors where possible.

Because there are no "early termination descriptor" on the 68 060. We
don't want the MMU to return any bus error. As in the original Falcon,
this job is devoted to the hardware (timeout).

This way a card in the CT60 expansion port will be able to use any
adress range without any modification in the MMU tree.

One can imagine the case of a card with some additionnal SD-Ram slots, a
PCI controler,... :)

Bye,
--
Xavier Joubert (Xaz) - Nantes (France) - mailto:xavier.joubert@free.fr
Falcon 030 + CT2b + 68 882, 14+32 Mo, 3.2 Go IDE, Mitsumi IDE 12x