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I have a Late 2013 15" Macbook Pro with discrete graphics.

According to this Apple support page: https://support.apple.com/en-us/HT206587 this model supports 4K 60Hz over MST.

I just purchased a Dell P2415Q monitor, which supports DisplayPort 1.2, MST, and 4K 60Hz.

I have the two connected by the included mini DisplayPort to DisplayPort cable.

And the monitor is running at 30Hz.

Everything I've read suggests that I should be able to get the monitor to run at 60Hz, but I can't find out how to. I'm trying to find answers among all the search results, but they're either outdated, different models, or asking about HDMI.

Can anyone assist me?

EDIT: Here's the monitor's display options, which show that I've turned on MST and where I'm getting that it's running at 30Hz:

Monitor options display

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    How can you tell it’s running at 30Hz? I have the same model MBPr, and dual P2415Qs. To me, the system utility says 1080p60, but I’m positive both of the monitors are running at 2160p (not sure about actual refresh rate). – NoahL Apr 28 '18 at 23:45
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    Hi @NoahL, I've updated my question with a photo of the in-monitor menu. I assume the bottom left it is current state? Also, I think I'm noticing a different between the mouse movement on the Dell vs the built-in display. – Jon W Apr 29 '18 at 0:25
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    Under system pref -> displays what is the resolution? Are you using “best for monitor” or “scaled”? – NoahL Apr 29 '18 at 0:27
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    @NoahL "Default for display." I should note that I'm running the the external monitor and the built-in display at the same time (I was under the impression that doesn't matter, but maybe it does?) – Jon W Apr 29 '18 at 0:29
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Okay so I got 60hz working at 4K. Despite the fact that I swear I already tried this, the key was turning off MST.

Unfortunately, I can't recall why I turned MST on in the first place. Did I create my own problem? I will say that I was unfamiliar with what Multi-Stream Transport was when I read the Apple support doc that I linked to in my question, and the doc was written in such a way to suggest that it was necessary for me to have on to get 60Hz on my MacBook Pro model.

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  • No, there's something flakey going on here. I had the exact same issue, with MST turned off (double checked). I then turned on MST (which gave me a black display), then turned it to secondary by pressing the green checkmark for 8 secs, and then still, no 60Hz. Tried two different cables: Mini DisplayPort (to USB-C, 2017 iMac) and regular DisplayPort (to USB-C), but no dice. Strangely enough, I have it working now by, once again, turning MST off, like you say. An lo and behold, despite nothing has really changed (MST was off, it is off now), it's running on 60Hz for the first time in months. – zmippie May 22 '18 at 13:45
  • May I know what cable are you using for the connection? Thanks – AGamePlayer Oct 29 '18 at 11:03
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I have a 15" mid-2015 MacBook Pro and had the same problem: my P2415Q monitor was running at 30Hz instead of 60Hz, despite being connected over DisplayPort. I'm not sure exactly what caused this problem in the first place: I had previously been using the monitor at 60Hz. But it seems to have gotten stuck at 30Hz after I unplugged from a different monitor. Initially, MST was set to Off.

I solve the problem by going under Menu -> Display and setting MST to Primary, then to Secondary, then to Off. Initially, MST was set to Off, so it is strange that this fixed the problem, but it did!

Now my monitor is running at 60Hz!

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