I meant to answer this earlier but I don't have anything to show what cable this is. I don't know and I guess I don't understand why the cable would make a difference. If you think I should buy the correct cable I will, maybe Best Buy or Staples.
I have five different miniDP > DP, miniDP > HDMI cables sitting in my office right now from trying to get full 4K UHD @ 60Hz on two different monitors. Suffice to say it took me a lot of cable switching and experimenting 'til I actually got it to work.