Subject: Re: Bad Mac OS ROM issues
From: Samuel Rydh (samuel@ibrium.se)
Date: Thu Jun 01 2000 - 11:14:14 MDT
On Thu, Jun 01, 2000 at 06:32:23PM +0200, Benjamin Herrenschmidt wrote:
> On Wed, May 31, 2000, David <dsmol@ddv.com> wrote:
>
> >
> >Symptoms were: increasing resolution beyond 800x600 would cause MOL to
> >crash hard - spewing information about loss of network packets followed by
> >lots of "adb buffer overflow" messages.
> >
> That's interesting. I did experience similar problems when trying to use
> large resolutions recently with both the 3.7 and 3.8 (MacOS 9.0.4 and
> "Ethernet Update") ROM images. I don't yet know if it's related to the
> ROM image itself or something else. I'm currently running on a different
> machine at 800x600 and it works very well.
>
> The symptom of the problem is the MacOS crashing (freeze) during
> framebuffer access, when re-painting the screen just after the resolution
> switch.
>
> I also noticed, with the latest MOL version, running at 800x600,
> occasional (but very rare) update "misses" (a video page was not
> correctly detected as dirty and so was not updated, causing a couple of
> lines beeing wrong on the display). This happened only once or twice in
> several hours and forcing a screen refresh fixed it.
>
> Samuel, could there still be some kind of race in the video driver or in
> the kernel-side page fault stuff ? The crash at high resolution also
> happened with full-screen video, which doesn't use the page-fault
> mecanism, so I'm not sure those two problems are actually related.
Perhaps. There shouldn't be, but the occasional video glitches
are indeed a strong indication.
I have also observed that when starting MacOS 9 using an
oldworld ROM, the resolution switch sometimes causes a
freeze (the problem goes if a single, fixed, resolution is used).
Thus there probably is a bug either in the video code or
somewhere in the MMU-code.
Cheers,
/Samuel
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