2015 mbp 13" retina scaling lag on 4K monitor

Discussion in 'MacBook Pro' started by laart, Feb 6, 2017.

  1. laart macrumors newbie

    Feb 6, 2017
    Hi, I just recently bought a new LG 27" 4K display (LG27UD68) for my 2015 13" Macbook Pro retina.

    It works flawlessly on the max resolution 3840x2160, but text and ui elements are just too small. It also works flawlessly on 1920x1080 resolution, but here everything shows much too large.

    However, when I try scaling it to something useful like 3360x1890 or 3008x1692 or even 2560x1440, everything on the LG display starts to lag, UI elements lag, you can feel some lag using the browser, photoshop and other programs. At the same time, everything on the Macs retina display runs smoothly even when the LG monitor is connected, same UI elements and browsers don't have any lag.

    I am running the monitor trough a DP 1.2 cable at 60 HZ. Previously I had a DELL 25" 2K monitor and it ran perfectly on the 2K resolution. Once I even connected two of these monitors and they both run without any issues at all.

    I have searched everywhere, but cannot seem to find any solution or even explanation for this problem.

    My laptop runs macOS Sierra 10.12.3.
    Specs: MacBook Pro (Retina, 13-inch, Early 2015), 2,7 GHz Intel Core i5.

    I would appreciate any help.

    Thank you.
  2. laart thread starter macrumors newbie

    Feb 6, 2017
    I have tried everything I could find, resetting all memories, changing cables, nothing has worked. Maybe my Macbook can't handle the scaling, which seems a bit weird?
  3. SarcasticJoe macrumors 6502a


    Nov 5, 2013
    The 13" machines have always had rather meager GPUs and I have a feeling that the scaling may just have been enough to make it so that the GPU no longer as enough oomph to produce content for both displays at 60 Hz, choosing to prioritize the internal display. However I'm not 100% sure about that so I'd suggest trying to run the MBP such that it only outputs to the external display to see if still lags, in which case it's something else, or if the lag goes away, which would support my guess.
  4. laart thread starter macrumors newbie

    Feb 6, 2017
    I had the same idea and tried what you suggested, but it didn't change anything. The lag was same either way. Now, I am running it at 4K resolution and compensating the tiny elements by zooming web browsers, office programs, skype and anything else I use on my work. It's not the best solution, but at least everything works smoothly and 4K display looks gorgeous. I might just get used to those small UI elements after some time.
  5. LCPepper macrumors 6502


    Aug 5, 2013
    United Kingdom
  6. Sanpete macrumors 68020

    Nov 17, 2016
    Must be like using a desktop full of icons!
  7. laart thread starter macrumors newbie

    Feb 6, 2017
    Thanks, I will make a backup and try the fix suggested in the second link tonight. It seems that it has helped several people, also some with 13" rMbp.
  8. SarcasticJoe macrumors 6502a


    Nov 5, 2013
    If it lags while displaying only to the external display it would seem like the problem is something other than just running out of GPU grunt. My guess after that would be that it's a software problem inside OSX.

    One last thing I'd ask you to look at would be what the OSX activity monitor shows when trying to scale the external display. Is the scaling tapping out the CPU or something?
  9. laart thread starter macrumors newbie

    Feb 6, 2017
    Activity Monitor also doesn't show any major increases in CPU or Memory usage while scaling. The system shows about 4-5% CPU usage both on 4K and on Scaled resolution.
    --- Post Merged, Feb 12, 2017 ---
    Unfortunately, this also didn't help, the lag is same as before. My guess now would be that Intel integrated video card simply cannot handle the scaling process?
  10. fhall1 macrumors 68040


    Dec 18, 2007
    (Central) NY State of mind
    Get a 30" 4K display and run it at max resolution - the pixels will be larger :)
  11. laart thread starter macrumors newbie

    Feb 6, 2017
    :D Looks like that would be the only solution to this problem.

    I have now used the monitor for about a week in 4K resolution and I can definitely say that my macbook has problems handling a bit heavier tasks. For example I can operate large excel files or photoshop files on the native 13" screen practically without any lag, but when I switch to the monitor, the problems appear - larger excel files have considerable lag when opened in openoffice or libre office, in photoshop I had to disable certain functions or else the lag made it unusable on the large screen.

    All in all, I believe that my 13" rmbp has too low specs to properly run a 4K monitor and I probably won't find any solution to this problem other than buying a new computer.

    (If someone finds this useful, here are full specs of my mbp - MacBook Pro (Retina, 13-inch, Early 2015), 2,7 GHz Intel Core i5, 8 GB RAM, 128 GB SSD, Intel Iris Graphics 6100.)
  12. werpu macrumors member


    Feb 1, 2017
    It could be, but it also could be the drivers, have you given bootcamp a shot to see if the performance is better in Windows?
    The problem is, Apple even for their ui uses a load of 3d functionality and has been doing that for ages. So if you have a weak graphics chip (which apparently all Intel based solutions have) and run it on high res then it might become problematic. But it also just could be the drivers hence I said give bootcamp a try. Windows drivers usually are extremely well optimized.
  13. laart thread starter macrumors newbie

    Feb 6, 2017
    This would be problematic, as this is my work computer and in that case I should buy a licence, which isn't an option for now. But thanks for the suggestions, I could try this in the near future.
  14. h37S3M macrumors newbie


    Nov 1, 2017
    My 15" rMBP (mid 2015) is having the same issue. It's too laggy with any type of scaling. I've resorted to not using my 4K monitor wit my laptop now. I'm basically settled on repurposing my 9-year old desktop to be dedicated to the 4K monitor.
  15. Trey M macrumors 6502a

    Trey M

    Jul 25, 2011
    OP, are you sure this is not related to the Hz (or refresh rate) which you have configured? I have a similar LG monitor and you have to enable a feature in the monitor settings to support full 60HZ (lag-free). Without this setting enabled, lag exists at 30Hz and it's not nearly as fluid of an experience.

    Can you check in the Display settings on MacOS whether you're running 30 or 60Hz?
  16. h37S3M macrumors newbie


    Nov 1, 2017
    I should check on that. But my guess is that the scaling not being a full 2-fold is more taxing on the GPU. Everything else looks like 60 Hz (mouse movement and stuff) but some stuff like video playback is very choppy on Youtube or some other place.
  17. j0shhh macrumors newbie

    Dec 7, 2017
    I'm having the exact same issue with a mbpr 13 2015 16gb 512gb... Max resolution works fine but every scaled resolution is laggy... Such a shame I've to use the monitor and zoom everything cause text are too small...
  18. buran-energia macrumors regular

    Oct 9, 2017
    The original poster says he has 3840x2160 and resolution scaled to 1080p works great. If your monitor's resolution is higher than 3840x2160 or if scaled resolution is not exactly twice as low, then chances are it's just too much to handle for the GPU in this model.
  19. j0shhh macrumors newbie

    Dec 7, 2017
    The default monitor's resolution is 3840 X 2160 which works fine but everything is very small. At 3008x1692 there is a delay and everything becomes slow. Photoshop lags a lot and my dev editor is very slow. At the moment I've decided to keep it at 3840x2160 and enjoy the space. 3008x1692 would be my ideal resolution. Maybe a mbpr with dedicated graphic card could support that resolution smoothly. I guess you're right it should be the gpu.
  20. Freyqq macrumors 601

    Dec 13, 2004
    Scaling is more taxing on the gpu. The only ones that aren’t are native res and half native res.
  21. Miltz macrumors 6502a

    Sep 6, 2013
    New York
    I think you're pushing it to the limit. According to Apple it doesn't support 4K at 60Hz so what you're saying makes sense. 4K/5K 60Hz is available on 2016 models.
  22. Fishrrman macrumors P6


    Feb 20, 2009
    "I think you're pushing it to the limit. According to Apple it doesn't support 4K at 60Hz"

    Where did you get this idea?
    The 2015 MBPro's DO support 4k @ 60hz.
    The right connection is needed.

    "The MacBook (2015 and later), MacBook Pro (2016 and later), and iMac (2017 and later) support these resolutions and refresh rates over HDMI 1.4b when using the USB-C Digital AV Multiport Adapter with macOS Sierra 10.12 or later:
    Up to 1080p at 60Hz
    3840 x 2160 at 30Hz
    These computers also support 60Hz refresh rate over HDMI when used with a supported HDMI 2.0 display, HDMI Premium Certified cable, and a compatible third-party USB-C to HDMI 2.0 adapter."

  23. buran-energia macrumors regular

    Oct 9, 2017
    What about 1920x1080?
  24. AdamJD macrumors member

    Mar 5, 2009
    Ran into this thread for the same reasons involving a mid-2014 MBP and AOC U2879VF. I didn't see the slow-up much until High-Sierra. It's unfortunate, but the only "solution" seems to be switching to 1920x1080 scaled which results into ridiculously large GUI elements or native res, which results in ridiculously tiny GUI elements. C'mon Apple. The mid-2014 retina pros went through years of issues due to buggy problems running YouTube on Safari (didn't even work right out of the box)...only to be hampered by new issues with High-Sierra.
  25. mj_ macrumors 6502


    May 18, 2017
    Austin, TX
    Putting the entire 60 Hz vs. 30 Hz aspect aside there's another reason for the stuttering. It happens because of the way macOS handles scaling. Let's assume we have a native 4K display at hand.

    At native 4K (3180x2160), macOS renders the image in 4K and projects in onto the display.
    At 2K (1920x1080), it quadruples each pixel resulting in a "native" 4K image that is then projected onto the native 4K display.

    However, as soon as you introduce scaling it gets much more complicated. Let's assume your scaling is set to 127% resulting in an effective resolution of 3008x1692. What macOS does now is to render everything at twice the scaled resolution (6016x3384) with quadrupled pixels, then scale it down to the display's native 4K resolution of 3180x2160 and project in onto the display.

    That's why, as soon as you enable scaling that isn't "Default" for the display in question, everything gets much slower. Now add a second screen into that equation (after all, every Retina MBP has an internal screen that most likely is also running at a non-Default scaled resolution) and it adds up. Intel's integrated GPUs are simply not powerful enough to handle that kind of graphics load.

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25 February 6, 2017