Stereo problems on a Mac Pro with 2 Cinema displays

1
I am trying to run the StereoDemo in Stereomode 10 for multi displays. I am using Matlab R2007a on a new Mac Pro 2.66GHz Quad-Core Intel Xeon. My video cards are two NVIDIA GeForce GT 120. Currently, the two cinema displays are connected to a single card. The cinema displays are the old model (23 inch).

While the StereoDemo works fine on my Macbook pro with a second display connected, I get the following error when I try to run it on the Mac Pro.

PTB-ERROR[ContextCreation failed: invalid share context]:The specified display may not support double buffering and/or stereo output. There could be insufficient video memory


PTB-ERROR[Low-Level setup of window failed]:The specified display may not support double buffering and/or stereo output. There could be insufficient video memory
2
Hi Mario,
Thanks for your advice - I am very relieved. Yes it was the dual video card issue. I had one display in each card - D'oh! StereoMode 10 works fine with just two monitors connected to the same video card. I haven't tried a third in the second card yet -- Mac's cables are too short for my current setup.

Cheers,
Phil
--- In psychtoolbox@yahoogroups.com, "Mario" <mario.kleiner@...> wrote:
>
>
>
> I assume you have more than 2 displays connected? In that case the demo is
> probably trying to display on the wrong displays. It is hard-coded to use
> screens 0 and 1, assuming a dual-display setup.
>
> If i have to guess, your desktop monitor (with the dock and menu-bar etc.) is
> connected to
> one GPU and shows up as screenid 0, whereas the two displays for stereo work are
> connected to the 2nd GPU and correspond to screens 1 and 2. In that case or
> similar cases, the hardcoded screenids 0 and 1 would try to open the left-eye
> window on your first GPU and the right-eye window on the 2nd GPU, which is a
> no-go.
>
> Apparently, "the worlds most advanced operating system", driving "up to eight
> displays in the fastest Mac graphics ever"
> (<http://www.apple.com/macpro/features/graphics.html>) (quote of the iPhone
> company), can't even share resources across different graphics cards, so
> whenever your 2 stereo display monitors are not attached to the same graphics
> card, it will bomb out with the "invalid share context" error message.
>
> I really wonder why they advertise 8 display support if they still can't get
> simple dual-display operation right even in Snow Leopard -- not speaking of
> Leopard which was an utter disaster on NVidia cards and it took them over 14
> months to fix that for Snow Leopard.
>
> Test which screenids the command Screen('Screens') returns? Probably 0, 1 and 2?
>
> Try if PerceptualVBLSyncTest([1,2], 10); works. It would try stereomode 10 on
> screens 1 and 2.
>
> Then you'll need to change the hardcoded values in the demos to make them work.
> Unfortunately it gets difficult to automatically select the 2 out of n displays
> on a n > 2 display setup, so the demos need tweaking.
>
> I hope that is the problem, because otherwise things get ugly. Let us know if
> this is the problem.
> -mario
>
>
> --- In psychtoolbox@yahoogroups.com, "philipmgrove" <philipmgrove@> wrote:
> >
> > I am trying to run the StereoDemo in Stereomode 10 for multi displays. I am using Matlab R2007a on a new Mac Pro 2.66GHz Quad-Core Intel Xeon. My video cards are two NVIDIA GeForce GT 120. Currently, the two cinema displays are connected to a single card. The cinema displays are the old model (23 inch).
> >
> > While the StereoDemo works fine on my Macbook pro with a second display connected, I get the following error when I try to run it on the Mac Pro.
> >
> > PTB-ERROR[ContextCreation failed: invalid share context]:The specified display may not support double buffering and/or stereo output. There could be insufficient video memory
> >
> >
> > PTB-ERROR[Low-Level setup of window failed]:The specified display may not support double buffering and/or stereo output. There could be insufficient video memory
> >
>