With XFree86-4.0.2-11.4.0 attempts to use xinerama on G400 (with x86) and G450 (with Alpha) graphics cards seem to go through motions but ultimately fail: ... (++) Xinerama: enabled ... (II) Loading /usr/X11R6/lib/modules/extensions/libextmod.a (II) Module extmod: vendor="The XFree86 Project" compiled for 4.0.2a, module version = 1.0.0 ... Xlib: extension "XINERAMA" missing on display ":0.0". Is xinerama just not compiled in these binaries?
I'm not sure. I've got both a g450 and a g400 here. I haven't tried the g400 yet, but I understand from David Dawes that the dualhead doesn't work properly. G450 doesn't work dualhead yet, nor with dri. These issues are being addressed with relative high priority though. I can't promise anything on the Alpha, but we might possibly see a fix for some of these issues at least on x86 soon. I'm awaiting driver updates from Matrox...
"dualhead" and "xinerama" are not exactly the same thing (even if they both use two monitors). In the first case you have two separate displays, and in the second one display but stretched across two monitors. Yes, indeed, dualhead does not work properly yet with XFree86 and without extra (binary only and x86) modules from Matrox. Note that even if one will try these Matrox modules, and dualhead works without any problems, one will get the same response, i.e. "Xlib: .... missing ..." if attempting to turn on xinerama.
An error message is the same on x86 with ATI R128 card; although this is not a card with double outputs so I do not now if this may even work there (two cards?).
Xinerama support is built into our XFree86 releases and works for me during testing.
In what sense "works"? I just tried 4.0.3-15 on x86 machine with G400 card and I have the same effect as before. That means that log files indicate that everything is ok if I use xinerama or two screens; only I have a blank screen when a monitor is hooked up to the second output. When in the past I tried Matrox binary modules I had not only happy logs but also a picture on both screens.