Chances Apple enabled 13" rMBP to run 4k/60Hz

Discussion in 'MacBook Pro' started by Thares, Jun 22, 2014.

  1. Thares macrumors regular

    Thares

    Joined:
    Feb 25, 2011
    Location:
    Dresden, Germany
    #1
    Hey guys,

    I know this is highly speculative, but maybe some of you have some experience with Apple withholding or sharing features.

    According to http://rene.rebe.de/2014-01-27/dell-ultrasharp-24-4k-up2414q-on-mac/ the current (late 2013) MacBook Pro 15" (Iris Pro) is capable of running a 4k display at 60 Hz. Also, someone tested this with the 13" (Iris) rMBP - it worked under Windows.

    So my question is whether you think Apple would 'give' the 13" the needed drivers to run a 4k display at 60 Hz - or not. I think, according to Intel the chipset in the 13" is not meant to run 4k/60 Hz. But I'm not sure about this.


    Looking forward to hear your opinions.

    Daniel
     
  2. TheIguana macrumors 6502a

    TheIguana

    Joined:
    Sep 26, 2004
    Location:
    Canada
    #2
    It's never gonna happen.

    It has nothing to do with official or not, it is a straight hardware limitation on the Intel hardware side of things for the 13" models. From Intel's official documentation:

    Code:
    Maximum supported resolution:
    H-Processors: 3840 x 2160 @ 60 Hz - 15" rMBP
    U-Processors: 3840 x 2160 @ 30 Hz - 13" rMBP
    All 13" rMBP have U class processors, all 15" rMBP have H class processors.
     
  3. Thares thread starter macrumors regular

    Thares

    Joined:
    Feb 25, 2011
    Location:
    Dresden, Germany
    #3
    Thanks for the explanation. I read that somewhere. But one user tested whether 4k/60 Hz worksfor the 13":

    'Mavericks - does not show hidpi modes (note: need to try ResolutionTab)
    Bootcamp - shows the monitor as 2 monitors running in portrait. Other than this, it works @ 60hz.'​
    So it seems, technically it works somehow.
     
  4. TheIguana, Jun 22, 2014
    Last edited: Jun 22, 2014

    TheIguana macrumors 6502a

    TheIguana

    Joined:
    Sep 26, 2004
    Location:
    Canada
    #4
    I am highly suspicious of the claim that someone was running 4k @60Hz on a 13" rMBP. From everything we know from Intel that just isn't possible with the chips used in the 13" rMBP.

    The highest I have seen anyone running the 13" rMBP at is 52Hz at 4k using SwitchResX manual settings - that is technically possible as it just hits the processors bandwidth limits. Beyond that you are exceeding the bandwidth available on a U-series chip.

    The Bootcamp method setup where it is acting as two separate monitors makes sense on paper but that is not 4k - it is cheating because you are using two completely separate display channels - the computer is outputting two completely different monitor outputs and outputting that as two separate DisplayPort channels. With 4k support on the 15" rMBP the system produces a full 4k image then splits it between two DisplayPort channels using MST to send to the monitor where it is reassembled as a single display output.

    From a numbers perspective:

    For this bootcamp thing you are effectively pushing two completely separate DisplayPort channels at 2160x1920 @ 60Hz but without any MST magic - thats ~8.33Gbit/s each. So the processors graphics is drawing two 8.33Gbit/s channels and then outputting that as two separate DisplayPort channels.

    This fits inside the max capacity of DisplayPort which is 8.64Gbit/s and is well under the maximum of about ~12.46Gbit/s official maximum per DisplayPort channel Intel has set for U-series processors (this is based on the max listed resolution at 60Hz of 3200x2000. However, pushing it to the limit the maximum throughput I have seen people successfully achieve is running 4k @ 52Hz (this uses ~13.83Gbit/s of bandwidth).

    To compare, on the 15" rMBP when you are pushing out 4k @ 60Hz the system is producing a 4k image with total bandwidth consumption of ~16.02Gbit/s, then using MST it splits this image into two DisplayPort channels and transfers it as one big DisplayPort signal over Thunderbolt 2. This is possible because H-series processors support at minimum outputting a ~16.02Gbit/s bandwidth consuming signal.

    Moral of the Story: If you need 4k @ 60Hz buy a Mac Pro, a 15" rMBP or wait for the next revision of the rMBP that might come late this fall - but more probably in January next year.
     
  5. Thares thread starter macrumors regular

    Thares

    Joined:
    Feb 25, 2011
    Location:
    Dresden, Germany
    #5
    Thank you very much your detailed explanation!
     
  6. Hieveryone macrumors 68020

    Joined:
    Apr 11, 2014
    #6

    Is there even a noticeable difference between 52 and 60
     

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