[wplug] compositing in metacity

[E. Brian Doran]

The new ATI drivers do not handle composite with multiple GPU's.  The catalyst 
version for their range of firegl enterprise cards now implements multiview 
to replace xinerama..

"As described by AMD, MultiView provides "the ability to utilize GPUs from 
multiple adapters on an independent multi-display desktop. It allows a user 
to configure, manage and use a MultiView configuration under Linux and allows 
OpenGL applications run on any displays driven by multiple GPUs." Right now 
though there are several caveats when it comes to the support. MultiView will 
only work on systems that contain two identical FireGL graphics cards that 
belong to the FireGL V3300, V3350, V3400, V3600, V3700, V5200, V5600, V7400, 
or V7700 series. With that said, no Radeon graphics cards are currently 
supported by MultiView. Additionally, MultiView is not compatible with Compiz 
and it will not work if you are using Xinerama with X.Org. Last but not 
least, the RandR 1.2 support that was added in Catalyst 8.9 is disabled when 
using multiple ATI graphics cards." 

So as it stands this issue lies with both vendors, but ATI seems to be more 
aggressive with solving the issue.  Currently with nvidia I have xinerama and 
OpenGL applications working working across 3 screens (1 large desktop), just 
not composite extensions (compiz).  

I hope both development parties, nvidia and xorg, come together for xrandr1.3 
as it looks like they might support multiple gpus, or rewrite X framework.


-Brian






On Tuesday 18 November 2008 9:07:54 pm Patrick Wagstrom wrote:
> On Tue, Nov 18, 2008 at 7:16 PM, Michael Semcheski 
<mhsemcheski at gmail.com>wrote:
> > On Tue, Nov 18, 2008 at 5:34 PM, E. Brian Doran <ebdoran at comcast.net>
> >
> > wrote:
> > > If anyone has any insight as to the progression of this topic please
> > > let
> >
> > me
> >
> > > know.  I had heard that xrandr1.3 may suppot multiple GPU's etc.  Also
> > > googles summer of code had an entry for getting this to work but I
> >
> > believe no
> >
> > > one was awarded.
> >
> > Interesting problem.  My low-end nvidia card has no trouble with two
> > monitors, but I have no idea how I would go about adding a third.
> >
> > We have a computer in my lab with 5 monitors on it using nvidia, but
> > alas, its Windows.
>
> The issue with the nVidia drivers is that the hardware makes it an
> either/or proposition.  You can have either compositing or xinerama, but
> you cannot have both, at least with the nVidia driver.  The xorg people
> point the finger at nVidia and nVidia points the finger at xorg.  In any
> case, using xinearama is essentially deprecated in favor of xrandr1.2 which
> does all sorts of wacky stuff, like rearranging monitors on the fly,
> partial monitor overlap, hotplugging output devices.  If you've ever had to
> give a presentation with a laptop, xrandr1.2 is a godsend.
>
> I'm inclined to believe it's nVidia's fault. The intel drivers and newer
> opensource ati drivers have no problem with this.