4k display support on MacBook Pro Retina 13“ vs 15”

Discussion in 'MacBook Pro' started by halfthelaw, Jan 7, 2015.

  1. halfthelaw macrumors newbie

    Jan 16, 2009
    Is there a difference in the 4k support of the current MBPR 13" vs 15"?
    * does Iris 5100/5200 vs NVIDIA GeForce GT 750M make a difference?
    * do either support connecting two 4k displays?

  2. jonisign macrumors regular

    Jul 7, 2007
    * Current MBPR 13'' supports 4K @ 30 Hz over Displayport and HDMI for a two screen option. Over DP it is possible to output 4K @ 52 Hz on one screen over Displayport, needs manual settings with Switchresx.

    * Current MBPR 15'' supports 4K @ 60 Hz over both of its Displayports.
  3. mcarling macrumors 65816

    Oct 22, 2009
    Do you mean over both ports (both ports are needed to drive one display) or over each port (up to two external displays, one display per port) or over either port (maximum of one external display, using either port)?
  4. Freyqq macrumors 601

    Dec 13, 2004
    I only know for the 750M 15" version. 4k uses both ports' bandwidth on the 15", so the other won't work. However, the HDMI will still work. At best, you can have this setup:

    1 4k monitor at 60hz - displayport
    1 4k monitor at 30hz - hdmi
  5. halfthelaw thread starter macrumors newbie

    Jan 16, 2009
    Thanks all! I went in to an Apple Store today and asked to try various laptops with the 4k display - the employees had no clue about 4k support, but were very obliging.

    What I've learned so far:

    1. all current MBPR models can drive a single 4k @ 30Hz over HDMI
    I was surprised at how laggy this felt - I was anticipating I could live with it (given that I'm not a gamer), but it was just too unbearable. :(

    2. The 15" MBPR comes in two flavors - Intel Iris Pro only (base model) and NVIDIA. NVIDIA can drive 4k @ 60Hz.

    So the remaining question is: can Iris Pro run at 60Hz, or is that NVIDIA only? .. time to dig deeper into the specsheet :)
  6. jonisign macrumors regular

    Jul 7, 2007
    According to Apple Specs, the 13 inch RMBP should only do 4K @ 30 Hz over HDMI. However, the ACTUAL specs for the CPU in these from intel specify a 450 MHz pixel clock over DP 1.2, which will get you almost all the way there... 52 Hz @ 4K. Looks MUCH better than 30 Hz!


    Actually, I don't believe this is correct. I think it depends on the transport mode you're using for the monitor. If it's multi stream transport (MST), then yes, maybe this is true. However, over single stream transport (SST, newly released monitors are supporting this) then I believe both 15'' rMBP thunderbolt ports should support 4K @ 60 Hz because they are both true Displayport 1.2 ports. I believe this is the case for both models (with and without nvidia's chip). However, driving two 4K monitors on the integrated graphics might be a bit sluggish...
  7. halfthelaw thread starter macrumors newbie

    Jan 16, 2009
    I took a look at the Intel specs here:
    And the MBP processor specs here:

    And taken together they seem to imply that a Iris 5100 + U-series processor => 30Hz refresh

    However, the 15" processor is HQ series => 60Hz refresh rate

    Where did the 52Hz come from? I haven't been able to find that.
  8. Freyqq macrumors 601

    Dec 13, 2004
    Nope. 750M version at least uses a bonded channel for thunderbolt. There is only enough bandwidth for 1 4k display.


    Look at some old threads with the search feature. This has been discussed before. The 13" rmbp can do 52hz at 4k, but you have to use 3rd party software to get it to work.
  9. jonisign macrumors regular

    Jul 7, 2007
    Ah, unfortunate! Sorry for my quick assumption that it should just work. I'd be curious as to what's going on with the intel integrated version–– if I had a second 4K display I'd try this on my 13 inch, so far I've just done 1 4K @ 52 Hz... just assumed that the other displayport would work the same way.
  10. Freyqq macrumors 601

    Dec 13, 2004
    4k at 52 hz might actually not disable the second thunderbolt port. My understanding is that this is the max bandwidth available for one port. 4k at 60hz has been tested on this forum in the past, and it disabled the second thunderbolt port because it needed the extra bandwidth.

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9 January 7, 2015