3

I recently purchased both a Dell P2715Q 27" 4K monitor and a 13" 2015 rMBP. The monitor is not recognized when I plug the laptop into the monitor via the monitor's provided DP cable (into either Thunderbolt port). When I plug in the laptop using the Monitor's HDMI cable, it shows up and can render at 4K, but only at 30Hz. I also tried plugging the laptop into another display with HDMI and that one also worked fine. Unfortunately, I don't have access to another display that has a DP port. My research prior to purchasing the laptop and monitor suggested that I should be able to connect them easy-peasy and get 4K at 60hz using either MST or SST signalling. However, I am very new to Macs, so my question is whether or not I need to do something special to get this to work? A Thunderbolt to DP cable perhaps? The monitor also has a miniDP port as well, do I have to use that? Did I somehow end up with a broken DP cable?

Any ideas?

5
  • is there a menu option on the display to force it into SST mode?
    – Alnitak
    Apr 10 '15 at 20:10
  • According to the manual for the display, it works in SST by default. And I can't find any settings in the OSD for the monitor to switch it to MST (in fact, the option is disabled).
    – syazdani
    Apr 11 '15 at 0:27
  • These are the instructions for changing the monitor to MST mode: dell.com/support/article/us/en/19/SLN296015/EN
    – syazdani
    Apr 11 '15 at 0:55
  • I hope you find an answer - I've got my rMBP 2015 on its way and I was planning to buy this same monitor to go with it!
    – Alnitak
    Apr 11 '15 at 7:16
  • 1
    Apparently 10.10.3 has improved support for 3840x2160 @ 60 Hz SST.
    – Alnitak
    Apr 13 '15 at 15:39
2

So oddly enough, 10.10.3 didn't seem to make any difference, but the supplemental update that came up yesterday (14D130a) on Software Update (http://9to5mac.com/2015/04/16/apple-releases-os-x-10-10-3-supplemental-update-to-fix-startup-issue/) fixed it right up. Now when I connect the display via Thunderbolt, it comes up at the native 4K resolution at 60hz running in SST mode. Thanks everybody for your help!

6
  • I'm pleased to say I just received my P2715Q and it worked out of the box on 10.10.3 with all updates applied :)
    – Alnitak
    Jun 17 '15 at 12:35
  • Thank you for your update. Could you please help sharing what are scale resolutions available on your 4k monitor? Thank you in advance! Jul 30 '15 at 0:23
  • @RatanachaiS. I'm not sure what you are asking for. I can definitely get the info for you if you point me in the right direction though :)
    – syazdani
    Jul 31 '15 at 13:57
  • 1
    @RatanachaiS.: the options are 1280x720, 1920x1080, 2560x1440, 3008x1692, 3840x2160. But please be aware of the OS X resolution scaling issue: forums.macrumors.com/threads/…. tl;dr, the non native and non-pixel doubled resolutions can be pretty laggy because of the way that OS X does retina resolutions.
    – syazdani
    Aug 7 '15 at 3:08
  • 1
    You are all lucky if it's working well for you. I have had a miserable experience. I have a 13-inch, early 2015 MB Pro Retina with a 3.1 GHz i7 & 16 GB of RAM, running Yosemite and now El Capitan. This monitor does NOT work with a thunderbolt/mini-dp cable at all. It has only ever worked with the supplied mini-dp to display port cable, but it capriciously often doesn't work. Thinking that it a cable issue, I got another one. However, it still frequently chooses not work. It's not a MacBook port issue, because it works fine with a Thunderbolt display, implying a Dell engineering problem.
    – Subfuzion
    Oct 7 '15 at 20:21
0

From Everymac

*This model supports a simultaneous maximum resolution up to 3840x2160 on two external displays via Thunderbolt 2. Alternately, it can support a single display up to 3840x2160 via Thunderbolt 2 and a single 1080p display at up to 60 Hz, 3840x2160 at 30 Hz, or 4096x2160 at 24 Hz via HDMI.

afaik, Macs don't do MST

1

You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .