Re: Q:040/060 MMU and Snooping

From: Doug Little <doug_at_innerworkings.co.uk>
Date: Thu, 11 Mar 1999 10:13:01 -0000

>Which brings be to a question: the Afterburner MMU tables are cyclic,
>in that, after a while, they basically repeat the first 16 MBytes
>of memory. Why is this?

The programmers couldn't be hassled writing a proper MMU controller.

>Also, when attempting use the data transparent
>translation register to access memory way outside any valid range
>(say, 0x80100000, with the local address base in the TT register
>set to 0x80), my Falcon invariably locks up. I expected a bus error.
>What gives?


When you transparently translate, the first thing that happens is your
cache begins recording access to all your hardware registers, which
results in bad reads. This kills your machine.

If you try to read beyond the valid locations, it probably causes a
processor exception that isn't handled by the OS, and again kills
your machine. I noticed most of these things when I was working on
the TK code.

Doug.
Received on fr. mars 12 1999 - 17:12:26 CET