Greg Newsome mugginz1 at gmail.com
Fri Jan 8 04:43:57 PST 2010

> > > GL makes it one degree harder still, because now you have to figure out
> > > how to implement TFP.  For indirect GLX, the server has to bind the
> > > pixmap (on some GPU) to potentially any number of DRI textures on
> > > arbitrary numbers of GPUs.  You can be lazy about it, of course, but if
> > > you do so you're making the inherent TFP sync problems even worse;
> > > presumably we want a TFP texture to have the same texels on all the GPUs
> > > it's used on...
> > 
> > At least with indirect GL it's possible to make it all work with a
> > suitably large hammer. I don't even know if AIGLX ever worked under
> > Xinerama though. Did it?
> Not even a little.  DRI1 turned itself off when Xinerama is active, DRI2
> probably does too.

Not sure if this is relevant but AIGLX has been used over a Xinerama enabled 
xorg server to provide composted desktop over multiple GPUs.

I've used his technique via a 9600GT and 9800GT bound via Xinerama with AIGLX 
on top, and while GLX isn't available to apps, "wobbly windows" and such 
performed across three 24" monitors with similar performance to two 24" 
monitors via Twinview.

His approach is documented here

My summary is here

More information about the xorg-devel mailing list