Created attachment 94656 [details]
Working dmesg (nouveau not in initramfs)

When the nouveau kernel module is embedded in the initramfs (as in ubuntu
14.04), Xorg fails to start on the secondary GPU. The DRM appears to correctly
initialize both cards (see attahced logs), but the monitor connected to the
secondary one never comes up. Apart from removing the module from the
initramfs, a workaround is to stop X and execute at the terminal:

echo 0 > /sys/class/vtconsole/vtcon1/bind
rmmod nouveau
modprobe nouveau

and restart X.