[ubuntu] fix HDMI overscan - 16.04 no catalyst control

How to fix HDMI overscan ? Desktop is spilling over screen edges.

After install I find out 16.04 LTS caot have catalyst control centre any more. I always used that to fix my overscan.
The monitor does not have an overscan option.

GPU Radeon HD5850
Monitor Viewsonic HD 1080p

I'd like to keep using the radeon card with the open source drivers but don't know how to fix overscan issue.

Something with xrandr ?

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