Subject: IIsi internal video MMU mapping problems
To: None <port-mac68k@NetBSD.ORG>
From: Martin Jerabek <jerabek@rm6208.gud.siemens.co.at>
List: port-mac68k
Date: 07/31/1996 09:59:13
Hi!

I installed NetBSD 1.1 on my IIsi a while ago and ran into the
seemingly well know problem that the kernel cannot boot when the
internal video is disabled (I normally use a SuperMac NuBus video card)
because of the different RAM bank mapping. With internal video all went
well.

Since I don't want to continuously plug and unplug the monitor when I
switch between NetBSD and MacOS (accelerated true color is really
nice!) and I also don't want to buy a second monitor, I'm willing to do
something about it (i.e. fix the bug/feature/whatever). I didn't check
recent kernels but I guess the bug is still present because it's still
on Allen Briggs' ToDo-list (finger briggs@puma.macbsd.com).

I do have UNIX experience but I haven't learned the internals of
(Net|Mac)BSD yet so I'm thankful for any hints or possible solutions.
The only solution I can think of currently is to change the MMU mapping
in the booter right before control is transferred to the kernel but is
this really possible without crashing the machine? As I understand it
the kernel must start at address 0 so just loading it into RAM bank B
and leaving the 1MB bank A unused won't work, right? Do other machines
have the same problems with the internal video (e.g. IIci which also
has non-contiguous RAM banks)?

Sorry if I sound clueless but I'm on this list for only a few days (I
did check the mail archive for July :-).

Bye,
Jerry

-- 
Martin "Jerry" Jerabek
mailto: jerabek@rm6208.gud.siemens.co.at
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