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Does anyone know if I can connect two 4k monitors running at 60Hz to my MBP 13" early 2015, 3.1 GHz Intel Core i7, 16 GB 1867 MHz DDR3, Intel Iris Graphics 6100 1536 MB). Specifically, I am interested in the DELL P2415Q.

My understanding is that I can connect 2 monitors with res 3840 x 2160 via the two thunderbolt ports, but only one can run at 60Hz, the other must run at 30Hz.

Any help is appreciated!


marked as duplicate by Tetsujin, fsb, Nimesh Neema, Allan, Glorfindel Sep 30 '18 at 12:54

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  • Could you please share your experience with P2415Q and MBP with Intel Iris Graphics? Can you confirm that with if one P2415Q is connected it runs at 60 Hz? – delirus Oct 29 '16 at 14:23

You can run one external display at 3840x2160@60Hz, or two external displays at 2560x1440@60Hz. There are two thunderbolt connectors, but only one thunderbolt controller, which only has the bandwidth of a single DP1.2 port. If you connect two UHD (3840x2160) displays, I'd expect both of them to run at 30Hz.

Contrary to my expectation, I have two UHD monitors running at 3840x2160@60 Hz connected to a Mid 2014 15" Retina MacBook Pro (MacBookPro11,3). Both external displays are Samsung U28D590 with DP1.2 enabled. There are two separate ways of displaying the resolution and refresh rate (the monitor's own report, and System Preferences), and for both monitors, 3840x2160@60 Hz is reported by both methods. To see all of the details in System Preferences, hold Alt (Option) while changing Default for display to Scaled, then select Show low resolution modes. With my displays, it doesn't allow me to change Refresh Rate, but it displays as 60 Hz on both displays.

On a separate note, I recently discovered that the Apple Store claims that a 27" Retina iMac can drive two external UHD displays at 60 Hz, or a single 5120x2880 display with dual inputs. When I first saw that I wondered whether the newest Retina iMac has a second Thunderbolt controller, but today's test on my Mid 2014 MacBook Pro suggests another possibility, a software improvement that somehow makes better use of the available bandwidth. I'm not convinced today's experiment would have had the same outcome a year ago, but I'm not quite tempted to install an older release and repeat the test (this MacBook Pro is running MacOS X 10.11.4 (15E65)). If anything, I'm more tempted to buy a Dell UP2715K to see if anything I already have can drive that.

I have neither a DELL P2415Q nor a 13" MacBook Pro to test, but based on today's experiment I'd say there's a good chance your Mac can drive two P2415Q displays at 3840x2160@60 Hz. Failing that, the second display can probably do 30 Hz with the HDMI port.

  • Yes, there should be -- but it is not an ideal setting 30Hz... any advice on 2K monitors? – user1497530 May 5 '16 at 1:20
  • I found this video youtube.com/watch?v=ak0_8dNohLE ,the guy run 2x4k at 30Hz with 2014 macbook pro. I am assuming the early 2015 will do better. – user1497530 May 5 '16 at 1:32
  • I wouldn't expect 2014 and 2015 MacBook Pro to have different video bandwidth. I believe they're both DP1.2 with a single Thunderbolt controller. – Eirik Fuller May 5 '16 at 15:28
  • Yes, you're right both have a single Thunderbolt controller with 20Gb/s bandwidth. Based on my calculation I need 24Gb/s to run two displays at 4k 60Hz. – user1497530 May 6 '16 at 12:15
  • Thanks a lot for the answer! Does it look good the 4k display scaled down to 2560x1440@60Hz?or it is not worth it? – user1497530 May 6 '16 at 16:08

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