Comment # 19 on bug 110865 from Martin

with 70W i mean total system power-consumption of course. 
This is roughly the same / a little more as with Windows. So we are on a good
path I think.

If i do 
"echo low > /sys/class/drm/card0/device/power_dpm_force_performance_level"
the flickering stops.
So the flickering is caused by the automatic powermanagement / reclocking.