Re: NetBSD 1.1 and Picasso - possible solution

["Markus Illenseer" <markus%tiger.teuto.de@localhost>]

George Harvey wrote:
> I had the problem on a standard 3000T but I have seen reports that it
> happens with some 4000s and accelerated 2000s. I have no idea why some
> systems have the problem while others work fine but I do know that
> changing the DAC access code has fixed the problem for me and hopefully
> it will work for the other cases as well.

 We need to distinguish between the "White-Screen" and the "Black-Screen"
Problem.

 The "White-Screen" problem only occurs on specific machines.  Regardless
which CPU or which Amiga, on these cards it happens that the Picasso is
correctly initialzed and works perfectly - but you only see a white screen
- a lifesign at least (White seagull on white screen, nice banner, everyone
immediatly surrenders on sight :-) This problem is assumed to be fixed with
the correct timing for the hidden DAC register.

 The "Black-Screen" problem was reported from A2000 with 040 accelerater
boards.  The black screen indicates that the Picasso failed to initialize.
This happens because due to the wonderfull "byte swap" (which is no swap,
but a "bug" in the Zorro to 040 interface), and results into the fact, that
the I/O-ports to the cirrus chip are not addressed correctly.  Klaus
Burkert tried to fix this problem in adding - at first view absolutely
useless - 0xffff to the port-adrresses.  The Zorro-to-040 interface will
then "translate" this attempt to access the port to the "correct" ports.

 Did I mentioned "magic" already?

-- 
Markus Illenseer