2015 MacBook Driving External 4k Display @60 Hz

Discussion in 'MacBook' started by SnakeP, Apr 27, 2017.

  1. SnakeP, Apr 27, 2017
    Last edited: Apr 30, 2017

    SnakeP macrumors newbie

    Joined:
    Oct 5, 2014
    #1
    Hi guys,

    I want to create this thread in order to help people like myself with their struggles to decide on an external 4k-display that's driven by a MacBook (early 2015). Since there are plenty of parameters (like HDMI vs. DisplayPort vs. USB-C, 30 Hz vs. 60 Hz, simultaneous charging of the laptop via USB-C etc.), I want to give an overview over the pro's and con's of each configuration, based on your input.

    I'm aware of some other threads in this forum (like this one) dealing with similar questions, however, I consider it a good idea to gather as much information as possible in a single thread.

    • LG 27UD88, 3840x2160 confirmed via USB-C, 60 Hz confirmed, charging confirmed (=> @andy9l)
    • Acer H277HK, 3840x2160 not confirmed, 60 Hz not confirmed, charging not confirmed
    • HP ENVY 27, 3840x2160 confirmed via USB-C, 60 Hz confirmed, charging confirmed (=> @ahostmadsen)
    • ...

    Looking forward to your input! :)
     
  2. andy9l, Apr 28, 2017
    Last edited: Apr 28, 2017

    andy9l macrumors 68000

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    Aug 31, 2009
    Location:
    England, UK
    #2
    Nice thread.

    LG 27UD88 via USB-C:

    3840x2160 - confirmed
    60Hz - confirmed
    Charging - confirmed
    HiDPI scaling - confirmed

    I use that monitor every single day with my 2015 rMB. Never had an issue.

    Performance is pretty poor on the 2015 rMB when driving a 4K display - especially when scaling. Wouldn't recommend for most.
     
  3. SnakeP thread starter macrumors newbie

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    Oct 5, 2014
    #3
    That's perfect, thank you! I just updated the list in the original post with your input. :)

    Could you please elaborate a little on the performance? Is the input (mouse) laggy? From the video you posted in the other thread it didn't seem too poor...
     
  4. andy9l macrumors 68000

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    Aug 31, 2009
    Location:
    England, UK
    #4
    Of course. All of the below is purely based on my experience and understandings. I've had my 27UD88 since November last year and my rMB since launch, April 2015.

    The MacBook is designed for short bursts of CPU power, and consistent low-power usage. This is completely by design and makes sense for the MacBook’s intended purpose - ultra portability and productivity on-the-go. It’s what makes the MacBook so good for a lot of people - myself included.

    Annoyingly, we live by the laws of physics - having a consistently hot component (CPU) inside a solid metal casing, using only a single piece of metal as a heat sync / cooling system ultimately leads to poor heat dissipation.

    Put simply, the longer the CPU stays hot, the hotter the surrounding materials become and the less efficient the cooling becomes. Very simple physics. This is when performance starts being impacted as the short-bursts of power are no longer possible - the CPU must throttle to avoid overheating.

    Driving a 4K display and running programs such as Photoshop or iMovie is enough - at least in my experience - to cause the scenario I’ve described above. As such, using a 4K display with your 2015 rMB eventually results in throttling and thus relatively poor performance. I find that scaling to 1440p @1.5x makes this happen even faster, presumably due to extra strain on the CPU for the scaling. Interestingly, running 1080p @2x does improve performance and delays the impact.

    The 2016 models have slightly improved graphics performance, so you may see better results from those. That said, I’m not convinced the difference is so great based on raw benchmark results.

    FWIW, I’m holding out for this years’ update, or the next MBP with a keyboard fix. I mostly use my gaming PC for browsing/time wasting in the evenings now. I’ve actually been pleasantly surprised by Windows. For work and my hobbies, though, I cannot do without macOS. Plus, I love Apple hardware.
     
  5. SnakeP thread starter macrumors newbie

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    Oct 5, 2014
    #5
    Thank you so much for your explanation, it all makes perfect sense of course.

    However, my use case for the MB is quite simple: bringing it to the office, working with it on trains and on customer's site. That being said, I want to have the opportunity to just plug-in an external display at home and charge it at the same time, whilst the lid is closed. I'm only using software that is easy on the CPU (like Outlook, Excel, Word etc.). It would be very interesting for me to know what the Activity Monitor tells you with the 4k display connected and everything else "idle"...
     
  6. ahostmadsen macrumors 6502a

    Joined:
    Dec 28, 2009
    #6
    Let me update:

    HP Envy 27": 3840x2160 confirmed via USB-C, 60 Hz confirmed, charging confirmed (2015 MacBook), but I use it in 1440p.

    All in all, I'm very satisfied with the HP Envy 27, especially after update to 12.2.4 (solved wake from sleep issues). It works, and the design is quite stunning. Only disadvantage is the lack of USB output ports, which depending on you usage, may matter or not.
     
  7. SnakeP thread starter macrumors newbie

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    Oct 5, 2014
    #7
    Thank you very much for the update! :)

    Even though you're using 1440p instead of "native 4k", did you experience any performance issues whilst trying 3840x2160?
     
  8. andy9l macrumors 68000

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    Aug 31, 2009
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    England, UK
    #8
    He's not really using 1440p. He's just scaling 3840x2160 to look like 1440p. I do the same, as do most with a 4K monitor.

    Doing this is actually more strain than just native 3840x2160.
     
  9. ahostmadsen macrumors 6502a

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    Dec 28, 2009
    #9
    Yes, exactly.
     
  10. SnakeP thread starter macrumors newbie

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    Oct 5, 2014
    #10
    Exactly, scaling is what I was referring to as well. By "native 4k" I ment driving a 4k display without scaling.

    Do the two of you use a special USB-C cable or does both, displaying and charging, work at the same time with any cable? I think I read somewhere that not every cable would be able to handle it?!
     
  11. andy9l macrumors 68000

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    Aug 31, 2009
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    England, UK
    #11
    I just use the cable that comes with the LG. Works perfectly well for me.

    The cable you get from Apple only allows for charging, not data transfer - so that one won't work.
     
  12. ahostmadsen macrumors 6502a

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    Dec 28, 2009
    #12
    I understand (from reviews) that you really can only use the cable that comes with the HP monitor. I wonder what will happen if you loose it...
     
  13. John William macrumors newbie

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    Apr 22, 2017
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    Canada
    #13
     
  14. brunelbushi macrumors newbie

    Joined:
    May 14, 2013
    #14
    Hi all,

    Just thought I would let you know that you can update this to read:

    Acer H277HK, 3840x2160 confirmed, 60 Hz confirmed, charging confirmed

    Got my display yesterday and am loving it so far.
     
  15. Sam347 macrumors newbie

    Joined:
    Aug 15, 2017
    #15
    I have major sleep/no wake up/have to reboot issues using a 13# 2017 TB MBP and 2 LG 27ud68 4K monitors via a USBC to DP with the original LG cables. Anybody can help with this bug ?
     

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