Is 4K @ 60Hz via HDMI even possible?

Discussion in 'Mac Accessories' started by Tex-Twil, Aug 9, 2018.

  1. Tex-Twil macrumors 68020

    Tex-Twil

    Joined:
    May 28, 2008
    Location:
    Berlin
    #1
    Hi,
    I have a 2017 macbook pro 13" and I'm trying to connect my 4K P2715Q screen via HDMI but the best I can get is 4K @ 30Hz. On my previous mac, I had the screen connected via a mDP cable and I could get 4K @ 60 Hz.

    When I use a USB-C to mDP adapter, it works fine but I already have some other USB-C hubs with HDMI ports and I'd like to avoid getting yet another adapter.

    Is 4k at 60Hz event possible?

    I found some DELL support pages about this topic but it does not help in my case. I also noticed that the screen itself reports 4K@60Hz

    IMG_1529.jpg


    while macOS only 30Hz

    Code:
    ~  $ system_profiler SPDisplaysDataType |  grep DELL -A 2
            DELL P2715Q:
              Resolution: 3840 x 2160 (2160p 4K UHD - Ultra High Definition)
              UI Looks like: 1920 x 1080 @ 30 Hz
     
  2. cynics macrumors G4

    Joined:
    Jan 8, 2012
    #2
    This is likely due to 4k 60hz WITH 10 bit color and no subsampling (4:4:4). Combined they will easily exceed the bandwidth of HDMI 2.0.
     
  3. jtara macrumors 68000

    Joined:
    Mar 23, 2009
    #3
    There are 4K monitors that don't support DisplayPort or Thunderbolt?

    I looked up your model, and it supports DisplayPort. Why do you want to use HDMI? (Something else connected to DisplayPort?)

    You just need a Thunderbolt 3 to DisplayPort (full size, not mini) cable.

    Tip: make sure you get one that locks in to the socket. The ones that don't easily fall out or become loose.

    You don't need an "adapter". Just a cable. Obviously though if you don't have a free TB3 port you may need to get another hub.
     
  4. HenryAZ macrumors 6502a

    HenryAZ

    Joined:
    Jan 9, 2010
    Location:
    South Congress AZ
    #4
    4k @60Hz is possible over HDMI 2.0 connections. Both the computer's and the monitor's HDMI ports must support the new HDMI 2.0 standard. My new Mini's HDMI port does, but my older Eizo EV3237's HDMI port does not. So I am using a Moshi cable (sold on the Apple store), that is USB-C --> Displayport to achieve full UHD @60Hz. On my older desktop, with the same monitor, I used a TB2 --> Displayport cable (with the TB2 acting as a Mini Displayport) running the same resolution @60Hz.
     
  5. jtara macrumors 68000

    Joined:
    Mar 23, 2009
    #5
    FWIW, I got that cable from the Apple Store, and returned it. It doesn't have the locking clip on the DisplayPort end.

    I replaced it with a CableMatters cable from Amazon that does have the clip. Much better cable, and a lot less expensive.
     
  6. HenryAZ macrumors 6502a

    HenryAZ

    Joined:
    Jan 9, 2010
    Location:
    South Congress AZ
    #6
    Personally, I've never found the need for locking clips, but I guess that could depend on how you have your monitors and computer situated. The Moshi cable is the first (and only so far) certified by VESA for 5k resolution. Mine works fine and stays put. I've been using Displayport input on my monitors for about 7 years now with no problems without a clip.
     
  7. jtara macrumors 68000

    Joined:
    Mar 23, 2009
    #7
    I think it matters if the port is situated vertically or horizontally. Horizontally is actually more of a problem. Gravity acts to angle the connector and then it starts working loose. Move your chair, tap your put, set a cup of coffee on the desk, and you'll get a glitch or worse, then you have to re-adjust the connector.

    I've had issues with this on both a Samsung 34" ultra-wide where cables plug straight in to the back. As well as with my 2012 Mac Mini. (Mini-DP in that case, and there no locking clip possible as it's not included in the design of Mini-DP.
     

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6 August 9, 2018