Question Bought new 144Hz monitor - when connected via DP weird things happen

Quarien

Commendable
Jul 30, 2019
2
0
1,510
So.
I bought Samsung CJG5 - a 2k/144Hz monitor.
I'm running a Zotac AMP GTX1070 (Also: Xeon X5670, Asus P6X58D-e).

I've connected the monitor via DP to the GPU and I have multiple issues.
Monitor defaults to 59Hz. Maximum refresh rate I'm able to select is 120Hz - which looks bad (something is off with the sharpness)
The setting within Samsung menu are grayed out - I can't even set the brightness.

When connected the HDMI cable - everything works fine!
However I can't use HDMI as I'm also running a TV connected to this port. So I'd like to stick to the DP port.

Right now I'm out of other cables, I might debug this DP cable, however it's brand new and it's labeled as 1.2.

What's the issue? How can I debug this?