Bonjour,
Ancien pocesseur de carte ATI et utilisant le driver radeon à l'époque (dernière utilisation il y a moins d'un an) je n'avais jamais pu activer le mode Xinerama avec ce pilote. Mais je m'en fichais, car je n'ai jamais aimé ce mode.
Par contre, là je viens de faire une recherche sur le net et apparemment il faut rajouter cette option dans xorg.conf pour pouvoir lancer le mode xinerama :
Option "MergedFB" "boolean"
This enables merged framebuffer mode. In this mode you have a single shared framebuffer with two viewports looking into it. It is similar to Xinerama, but has some advantages. It is faster than Xinerama, the DRI works on both heads, and it supports clone modes.
Merged framebuffer mode provides two linked viewports looking into a single large shared framebuffer. The size of the framebuffer is determined by the Virtual keyword defined on the Screen section of your xorg.conf file. It works just like regular virtual desktop except you have two viewports looking into it instead of one.
For example, if you wanted a desktop composed of two 1024x768 viewports looking into a single desktop you would create a virtual desktop of 2048x768 (left/right) or 1024x1536 (above/below), e.g.,
Virtual 2048 768 or Virtual 1024 1536
The virtual desktop can be larger than larger than the size of the viewports looking into it. In this case the linked viewports will scroll around in the virtual desktop. Viewports with different sizes are also supported (e.g., one that is 1024x768 and one that is 640x480). In this case the smaller viewport will scroll relative to the larger one such that none of the virtual desktop is inaccessible. If you do not define a virtual desktop the driver will create one based on the orientation of the heads and size of the largest defined mode in the display section that is supported on each head.
The relation of the viewports in specified by the CRT2Position Option. The options are Clone , LeftOf , RightOf , Above , and Below. MergedFB is enabled by default if a monitor is detected on each output. If no position is given it defaults to clone mode (the old clone options are now deprecated, also, the option OverlayOnCRTC2 has been replaced by the Xv attribute XV_SWITCHCRT; the overlay can be switched to CRT1 or CRT2 on the fly in clone mode).
The maximum framebuffer size that the 2D acceleration engine can handle is 8192x8192. The maximum framebuffer size that the 3D engine can handle is 2048x2048.
Note: Page flipping does not work well in certain configurations with MergedFB. If you see rendering errors or other strange behavior, disable page flipping. Also MergedFB is not compatible with the UseFBDev option.
The default value is undefined.
Je vous laisse tester !
Il y a d'autres options décrites sur ce site (xinerama, ainsi que la 3D)
http://www.thinkwiki.org/wiki/Additional_options_for_the_radeon_driver#Using_Xinerama
Pour info, il suffit de faire en ligne de commande
man radeon
pour avoir la liste de toutes les options (tout simpement !).