Comment # 16 on bug 64850 from Jakob Nixdorf

I checkt again when the second monitor is switched off.

I booted with radeon.modeset=0, which caused the radeon module to not be loaded
since I don't have UMS support in my kernel. With this both monitors work and I
can get a TTY on both.
But as soon as I run 'modprobe -v radeon modeset=1' the second monitor is
switched off to black.