Macbook Pro 16 with LG UltraFine 5K Display lags.

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Macbook Pro 16 with LG UltraFine 5K Display lags.

My Macbook PRO 16 lags when connected to the LG UltraFine 5K Display. It lags at any moment. I can have any application running and lags. I have tried changing the Display settings (at Default for Display LG-Ultrafine color profile --installed the LG driver app from the App Store), tested charging my macbook both through the monitor and with its charger, and still lags. I installed iStat Menus and can see NO application is hogging the GPU to make it lag. The track mouse jumps far away as if it had a spring, it holds back and then suddenly jumps further away from where I intended to take it. Video playback (youtube or Quicktime) lags and/or sound just stops for half a second. None of this happens when I disconnect the monitor.

I have a MacBook Pro (16-inch, 2019), 2.4 GHz 8-Core Intel Core i9, 64 GB, 8TB SSD, MD Radeon Pro 5500M 8 GB. Monitor is the Apple recommended LG UltraFine 5K Display 27MD5KL-B.

Any ideas?

MacBook Pro 16″, macOS 10.15

Posted on May 27, 2020 8:18 PM

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Answer 1

brenden dv

Community Specialist

May 28, 2020 12:54 PM in response to JoKrone

Hi JoKrone,

I understand that your Mac is having trouble when running your LG display, and I want to help.

Can you try starting to safe mode to see if you have the same behavior exhibited?

How to use safe mode on your Mac - Apple Support

Thanks for using the Apple Support Communities.

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Answer 2

May 28, 2020 1:54 PM in response to JoKrone

Mouse-cursor position update is done by the CPU, in the background, at low priority. The thing that makes it "jump" is not having time to re-draw the cursor frequently enough.

Counter-intuitively, if your main Processor -- that's CPU, NOT Graphics processor -- is busy, the cursor will jump. It's generally not a graphics problem at all.

The only case where this is graphics-related is if you are using a Dock with a "legacy" display Interface, and the Dock uses DisplayLink technology. This is because DisplayLink provides a simulated, un-accelerated display rather than using the graphics card Display Generator..

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Answer 3

JoKrone Author

Level 1

10 points

May 29, 2020 6:42 AM in response to brenden dv

Ok, I'm submitting this entry from Safe Mode, and this is what I'm experiencing: Mouse movement is choppy, Menus and Dock navigation also very choppy. Bringing up the Applications pane from the Dock has a 1 sec delay and scrolling thru the apps in the Application pane responds slowly and fires up the fans (very high). I started the LG Screen Manager (recommended by LG and downloaded directly from the App Store) and it seems to slightly improve, but not by much. Starting Safari (the only App I started fans began to kick up again.

Tested removing the monitor and raising the laptop screen and I can't sense any improvements.

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Answer 4

May 29, 2020 4:13 PM in response to JoKrone

JoKrone wrote:

...

Tested removing the monitor and raising the laptop screen and I can't sense any improvements.

...

That uses the Integrated Intel GPU instead the Discrete GPU, so that affirms you do not have a GPU problem.

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Answer 5

JoKrone Author

Level 1

10 points

May 29, 2020 4:46 PM in response to Grant Bennet-Alder

That was in SAFE MODE - With and without monitor was horribly slow - everything lagged. In NORMAL boot mode when the monitor is hooked up it sporadically lags, and when I don't have the monitor connected it doesn't lag.

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Answer 6

JoKrone Author

Level 1

10 points

May 29, 2020 5:19 AM in response to Grant Bennet-Alder

Yep, I purposely left out CPU, it was cruising at 4%. It's not CPU performance issues. The monitor is connected directly thru Thunderbolt 3. Recommended by Apple as monitor option in the Apple Store.

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Answer 7

JoKrone Author

Level 1

10 points

May 29, 2020 7:10 AM in response to brenden dv

In other words, it gets worst in Safe Mode

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Macbook Pro 16 with LG UltraFine 5K Display lags.

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