On Wed, 13 Dec 1995, Bernd Limbach wrote:

> Hi Steve!
> 
> 
> > pursuing this.. A2000 + 040 + Picasso = wierd problem! )
> 
> This seems to be a general problem,  is  it?  I  am  asking,
> because I have such an configuration here, but I am not able
> to see anything on my Picasso board via NetBSD. :(

Something very strange is happening to values of data as 
they cross to the Picasso VDAC regs.  During initialization,
the board does not get initialized properly.  

By playing with the VDAC_xxxx, you can succesfully get data to
the card, and even get patterns to show up on the display,
but resolution modes and colors are hosed..

The real stickler is that with the GVP GFORCE, there doesn't
seem to be any real pattern- I've gotten many good
looking, predictable displays, but they change from boot-to
boot..  This suggests that something is "missing" from 
(at least) the initialization..

With zippo support from GVP and lack of good documentation
from VillageTronics and Commodore 68040.library routines, we
are just poking in the dark (literally), randomly and hoping to
find some pattern or sense from the results...  This is 
especially frustrating since it appears to be a hardware 
inconsistency that has already been worked out by someone on the 
WorkBench side..

For now, all we know is that data sent to VDAC registers and
VDAC register addresses are "changed" when they cross from the
'040's memory/registers, across the ZII bus, and into the
Picasso.  The answer lies in "massaging" or "translating" 
prior to writing (if A2000 & 68040 & PICASSOII )

And unfortunately, "The Great Tao of Programming" hasn't been
looking my way..   (YET!)     ;)

Cheers!

----------------------------------------------------------------------------
Steve Paul,  McCue Systems, Inc.               	              Unix/VMS/C/C++
stevep@mccue.com 					       SUN/AMIGA/DEC
xeglon@shell.portal.com	  "If at first you don't succeed, redefine success."

Note: The opinions expressed here are my own and do not necessarily reflect
the views of my employer.