Subject: Re: MRG Disabling (and PB180)
To: Colin Wood <cwood@ichips.intel.com>
From: Michael R Zucca <mrz5149@cs.rit.edu>
List: port-mac68k
Date: 11/19/1997 18:45:22
> This is definitely the video mapping problem (since that's pretty much
> part of what occurs next).  If it were an ADB problem, you'd hang much
> later in the boot sequence (after the copyright message, during ADB
> initialization).

Yep. I sent many an hour finding out exactly what was happening in that gap.

> Yes, he did.  Of course, figuring out the "right way" is the hard part :-)
> There are actually a fair number of machines which will depend on this,
> including all of the PowerBooks, the Classic Macs, and the Quadra 605, to
> name a few.

(This is from ancient memories of mine)
Well, it looked to me like we were screwing something up in pmap_bootstrap.c
and machdep.c.

The 160/180's were particularly susceptible to a bug in pmap_bootstrap.
If I remember correctly, when we boot with intvid pmap_bootstrap twiddles
with the way memory is mapped. When we boot serial, all of that behavior
is side-stepped and we just inherit the mappings from MacOS.

To fix the 160/180's I simply put in a hack that did the serial mapping
if it was that particular model. However, what we really need to do is
figure out how memory is *really* mapped on every machine and then go
back and fix our memory mapping code.

And it's not just broken 160's and such that need this fix. It's machines
like the IIvx that we have "working" but occasionally weirdo stuff happens
(i.e. certain kernel sizes cause SCSI problems)

Scott, are you hearing this? :-)