Is running a 4k display at 1440p going to noticeably degrade performance no matter what?

Discussion in 'MacBook Pro' started by circa7, Apr 19, 2018.

  1. circa7 macrumors regular

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    #1
    I'm a graphic designer and use apps like Sketch, Photoshop, Illustrator, etc. I notice when I'm working on complex files, my 4k display has noticeable refresh issues as the GPU is constantly playing catch up with what I'm doing. I'm connecting directly via DisplayPort @ 60hz. Normal computer usage is fine (web browsing, videos, document editing, etc).

    I've been using a 2015 rMBP (2.5 GHz i7, Radeon R9 M370Z 2GB GPU) and had to switch to a 2k display since it was affecting my work too much. So, I went ahead and bought a brand new maxed out 2017 rMBP (3.1 GHz i7, Radeon Pro 560 4GB GPU) hoping the newer chips would be much better. It's slightly better, but definitely not $3,000 better.

    Running the display at native 2160p or 1080p works fine on both machines. But the former makes the UI unusably small and the latter doesn't give me enough screen space. So– is MacBook hardware just not powerful enough to scale a 4k display at 1440p without a noticeable performance hit? Or could it possibly be my display (LG 27UD69)? I've tried multiple cables to rule that possible issue out.
     
  2. casperes1996 macrumors 68040

    casperes1996

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    #2

    I don't know which it is, but if you'd like it to just be 2560x1440 (not scaled in Retina mode), performance should be better than 4k mode. Select it by holding Option when clicking "Scaled" in the Display section of System Preferences, then click the checkbox that allows low-DPI resolutions.
     
  3. circa7 thread starter macrumors regular

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    #3
    I've tried it on low-DPI but it's extremely blurry
     
  4. casperes1996 macrumors 68040

    casperes1996

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    #4

    Well..... That's how a 2560x1440 screen would look at that size - Assuming your display's scalar chip is handling the signal properly
     
  5. circa7 thread starter macrumors regular

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    Right, but then why wouldn’t I just use my 2k Display? I’m talking about hi dpi scaling. I’m guessing the MacBooks just aren’t powerful enough to do this with high performance unless I’m somehow not setting it up properly (which I think I am).
     
  6. csurfr, Apr 19, 2018
    Last edited: Apr 19, 2018

    csurfr macrumors 68000

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    #6
    There is no reason whatsoever that your machine shouldn’t be able to handle that display at that resolution. My iMac has essentially a lower version of that same GPU and it drives the 5k screen flawlessly. Also, my 2017 MbP has done the same with both the 4k and 5k UltraFine, in all of the apps you have mentioned.
     
  7. circa7 thread starter macrumors regular

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    #7
    It works fine if I'm working on files that are fairly simple. But if I open a large Sketch file, for example, that has a lot of gradients, shadows, artboards, etc., it's pretty slow. I'm connecting directly via DisplayPort @ 60hz.
     
  8. csurfr macrumors 68000

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    #8
    Unfortunately I don't have any rather large Sketch files to test for you on my machine. . . I've downloaded the iOS assets from a few different places (Apple and others) and while those are about 120mb or so, they don't seem to tax my machines too much. How large are you talking about?
     
  9. circa7 thread starter macrumors regular

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    I actually think the complexities of the colors/shadows are what impact performance the most.
     
  10. casperes1996 macrumors 68040

    casperes1996

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    #10
    Sorry, when you say 2k, do you mean QHD (2560x1440)? When I hear 2K, I think DCI-2k (Digital Cinema), which is 2048x1024 (and other variations starting with 2048).

    Right, first off, what iMac has a lower end version of that GPU with a 5k panel? Even if it has the same model number, bear in mind that the GPUs in iMacs have much higher core frequencies.

    Second; In terms of how hard it is to handle, 5K = 4K at 2560x1440 scaling. I know that's also the comparison you made, but I just wanted to add it for clarity's sake.

    My iMac has an R9 M295X in it, and it runs really quite well. There can be some frame drops if I'm taxing the GPU with games whilst trying to multitask, or rendering in FCP X (though that's surprisingly rare), but nothing big.
    I will say though that I suspect the size of the frame buffer to be a big factor with resolutions this large. Just running the desktop and random non-GPU accelerated apps essentially eats up like 1GB of VRAM on a 5k screen. With a GPU that only has 2GB of VRAM that doesn't leave much left for apps.
     
  11. circa7 thread starter macrumors regular

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    #11
    Yes, 2k I'm referring to a standard 1440p Thunderbolt Display. I'm scaling a 4k display to 1440 which is giving me the issues on the MBP. I'm assuming this is just due to the GPU having to do extra work since the OS is essentially rendering the screen at 5k and then cutting that in half. I understand that a 5k display at 1440 would work perfectly since it's exactly 50% of the max resolution.
     
  12. csurfr macrumors 68000

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    #12
    I'm not 100% sure as to the clock speed, as I've not seen the numbers. But, my 2017 5k iMac has the Radeon Pro 570 w/ 4gb of VRAM (I originally thought it was the 560). The 2017 MacBook Pro has a Radeon Pro 555 w/ 2gb or the 560 w/ 4gb, which certainly has to be comparable, don't you think? Has Apple in fact lowered the clock speed of the MbP graphics as opposed to the iMac? I wouldn't think they would do that. ¯\_(ツ)_/¯
     
  13. casperes1996 macrumors 68040

    casperes1996

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    #13

    Uhmmm. The OP in this thread has an R7 M370X.... Which is definitely a lower end chip.

    570 is a beefier GPU than the 560.
    Furthermore, all OEMs change clock speeds on one or more components for at least one of their designs. The iMac's cooling can handle more power, thus can run GPUs faster. It's not that they do it to slow down the MBP. It's that they make the clock speeds match the thermal headroom of the device. What AMD and Nvidia ship, is called "Reference" for a reason. It's not how it has to be, just a reference point so you know what the cards are guaranteed to be able to do.
    --- Post Merged, Apr 20, 2018 ---

    I don't think it's that your GPU can't handle it in terms of compute power actually. I think however that it may be running out of VRAM.

    Actually, if you open up Activity Monitor, and in the menu bar, select "Window" you can open up a panel that shows how hard your GPU is being pushed, the GPU history panel. That should give you some idea.
     
  14. Samuelsan2001, Apr 20, 2018
    Last edited: Apr 20, 2018

    Samuelsan2001 macrumors 604

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    #14
    Laptops are smaller and slimmer and have far less cooling capabilities this is referred to as TDP (thermal design parameters/point or power). You have to scale your components to work within the thermal abilities of the computer. Laptops by necessity just haven’t got the ability to run the most powerful graphics without dreadful battery life huge size and big heavy fans making a lot of noise. If that’s what you want then there are huge gaming laptops out there that can approach the performance of graphics cards in desktops but those aren’t the trade off that Apple chooses for its notebook design.
     
  15. csurfr macrumors 68000

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    #15
    The OP says he went out and bought a 2017 with the Radeon 560. That’s what I was referring to, not his older machine.
     
  16. casperes1996 macrumors 68040

    casperes1996

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    #16

    Sorry, I lost track of the thread a bit and just skimmed the first post until I saw a GPU part number. My mistake
     
  17. circa7 thread starter macrumors regular

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    Yeah, that’s what I meant. Just surprising that the newer card with twice the vram has comparable perceptive performance (m370x 2gb vs R9 4gb)
     
  18. casperes1996 macrumors 68040

    casperes1996

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    #18

    Hold on, I also missed the 4GB thing. My R9 M295X in my iMac is 4GB too and it can run graphically intensive applications without hitching in the UI (at least not majorly. Minor hitching can happen)
     
  19. circa7 thread starter macrumors regular

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    #19
    Maybe I'm just used to the 100% fluidity of my Thunderbolt Display. I guess I'll just have to decide if it's worth it for the slight hitching.
     
  20. Jago macrumors regular

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    #20
    What you want is to use SwitchResX to ”invent” a suitable virtual resolution that when scaled down to fit your screen will display the UI elements in your desired size. If you just run a 4K screen at a lower resolution, your actual performance will be much better, since there are less pixels to render, but your visual fidelity will suffer greatly, since the monitor will be doing rescaling and monitors are generally rather crap at doing it.

    I had this problem when I had a Mac attached to a 2560x1440 27” screen. The UI elements would looks so tiny, my eyes would start hurting after 30 minutes of use. But SwitchResX alllows you to ”invent” virtual resolutions. So I would create a 1920x1080x2 ”retina resolution”, which ScaleResX would then scale in software to perfectly fit the actual screen real estate. Works beautifully.

    This was perfectly doable on a 2012 Mac Mini with HD4000 GPU without any noticeable performance issues, unless you tried to play games using this massive resolution obviously.
     
  21. circa7 thread starter macrumors regular

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    #21
    Interesting... I never knew you could do an "x2" with SwitchResX. I'll have to check that out.
     
  22. ixxx69 macrumors 65816

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    #22
    Are you using the latest versions of those apps?
    SwitchResX isn't necessary for this. Jago doesn't appear to understand how macOS display scaling works (no offense intended toward Jago - most folks don't understand it).
     
  23. Jago macrumors regular

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    #23
    You can use the resolution options provided by Apple if any one of them suits you and you have a 4K or higher res display. The problem is that Apple hides a lot of perfectly workable resolution options ”just because” and you can use SwitchResX to create and apply them. Where SwitchResX is invaluable is when you are using a non-retina display - since stock MacOS then only offers your non-native resolution options where your display will be playing the rescaler and it will look like crap unless you stick with native res.
     
  24. ixxx69 macrumors 65816

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    #24
    But the OP is using a retina display, so none of that has anything to do with the issue. I understand the merits of SwitchResX, it's just what you're suggesting isn't applicable to the issue as far as I can see. But sorry if I misunderstood you. ;)

    Cheers!
     

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