Re: Booting original iMac

[Michael <macallan%NetBSD.org@localhost>]

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Hello,

On Mar 12, 2010, at 8:55 AM, John D. Baker wrote:

> OK, not quite as straightforward as I thought.
>
> On powerup, booting any NetBSD (4, 5, or -current) with machfb enabled
> trashes the screen as described previously.  It will do this every  
> time
> until...
>
> If I boot MacOS X, any resolution, as long as the color depth is set  
> to
> "thousands" (16-bit) (or less?  I haven't tried.) and then simply  
> restart
> (not shut down), subsequent booting of NetBSD with machfb enabled  
> works
> fine.
>
> ofb or genfb work fine without such subterfugue.  genfb (5, -current)
> clears the screen on attach as well, so I can't see any additional
> previous kernel messages before the machine hangs.  I'll rebuild a
> kernel with ofb instead of genfb (and disable machfb for the time
> being) to try to get more visibility into the hangs.

Or try a -current kernel - it will replay the message buffer when a  
framebuffer driver attaches.
So, it looks like your iMac wakes up in something else than 8 bit  
colour depth ( unlike all my machines ) and machfb always seems to  
assume 8 bit. That would at least explain the garbage you're seeing.
In order to confirm or contradict please do the following:
- - cold start the iMac and check what's in the graphics chip's depth  
property ( do 'dev screen', then '.properties' )
- - boot OSX, drop back to OF, check the depth property again
I might have to add code to either let machfb deal with colour depths  
other than 8 or make it switch to 8 if necessary.

have fun
Michael

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