Thank you very much, it solved perfectly my problem using :
Code:
sudo nvidia-xconfig --base-mosaic --metamodes="GPU-0.DFP-0:1280x1024+0+0,
GPU-0.DFP-2: 1920x1200+1280+0, GPU-1.DFP-0:1280x1024+3200+0"
The only point is that ligthdm is buggy so I use gdm (otherwise, any desktop manager fails).
Very Happy this morning
