One Mini DisplayPort yields small picture, the other works fine

Question

I have 1 DVI, 1 HDMI and 2 Mini DisplayPorts in my graphics card. I have a TV hooked up to the HDMI port, and two displays connected to the Mini DisplayPorts (with HDMI-mDP cables, because i have no mDP input on my displays). The setup works fine except for some reason one of the mDP ports yields a smaller picture compared to it's sibling.

As you can see on the screen to the left, there's a big black border to the picture (it's the same on all sides). The one next to it displays correctly.

Only one port yields the small picture. I have tried only connecting one display to the "faulty" port (tried both displays), it does not matter. I also tried switching cables.

I'm using an ATI Radeon HD 6950 graphics card. I can't find anything related to this in the Catalyst Control Center, and i can't seem to find anyone else having the same problem.

Is my graphics card defect? Is this a mDP limit of some sort?

Edit: All displays are running on 1920x1080, in case that matters.

Edit: Ended up using a DVI port for my second monitor instead. Assume the mDP port is broken.

Answer 1

The problem wasn't with the port, it was a setting in AMD Catalyst Control Center. The setting is in here:

My Digital Flat-Panels > Scaling options

Select the faulty display in the dropdown and drag the scaling slider to 0% overscan. Voila.