MacBook Pro 2018 with 4k Monitor input lag

[Tex-Twil]

Hi,
I've been trying for a while to run a 4K screen at a 200% scale (i.e 1080p retina) but I always have the same problem. When I type on they keyboard or use the mouse, there is a very small but noticeable lag. The interaction is definitely not so smooth as when using a 1080 or 1440p screen.

I start to wonder if it is even possible to have this resolution (4k @ 1080) without any lag.


I'm not talking about gaming at all, just a usual developer typing in a IDE (XCode, Slack, IntelliJ, AndroidStudio).
Here are some facts
- I tried different 4k screens (DELL P2715Q, LG 27UD58p)
- I tried different MacBook Pros: MacBook Pro 15-inch, 2018 with Radeon Pro 555x and 560x
- The screens were connected via USB-C to miniDP adapter -> DP cable -> screen and the refresh rate is 60Hz
- When using a 2k or 1k screen, everything is smooth
Any tips or comments?
- I do want to use the scaled down resolution as 2k or 4k is too small for me

I read in some other posts that the USB-C -> mDP adapter or a cheap cable could be the problem.

I'm thinking about selling the 4k screen and going back to 1080p as I've had this issue for years.


Any tips?

 

[nudoru]

Something is definitely wrong, but I'm afraid I don't know what it is. I've used several 4k monitors with varying scaled resolutions and have never seen this behavior.

I would try another cable, usbc -> mDP and see if that helps? But at 60hz, I don't know.

 

[Tex-Twil]

I ordered a new usb-c -> display port cable to see if that helps. If not, I will try the Apple's adapter thunderbolt 3 -> thunderbolt 2 adapter

 

[perelin]

I had similar problems. BenQ 4k display on scaled resolutions introduces very heavy lag for my Satechi bluetooth keyboard. Mouse was also a bit laggy, but bearable. Tried the default Apple Magic Keyboard, a bit less lag but still almost unusable.

What helped was a tip I found on reddit: https://www.reddit.com/r/mac/comments/6m6b2g
>> Turn on "reduce transparency" in accessibility settings

Now a bit of lag is still there, but it feels usable to me.

 

[Tex-Twil]

I'll give it a try, thanks

 

[yAak]

At work I have a Dell U2718Q and a 2019 MBP 15" Radeon Pro 560X 4 GB with the same issue.

Trying to do dev work, and even just having only a text editor open with the resolution unscaled makes typing laggy enough to be aggravating.

>> Turn on "reduce transparency" in accessibility settings

This DID help me some! Thank you, @perelin !

@Tex-Twil please report back on your results with a different cable. This problem is driving me crazy.

(I'm using the HDMI-to-HDMI cable that came with the monitor to a 3rd party USB-C adapter... I'm afraid its the UCB-C adapter, but don't want to throw money at the problem just yet.)

 

[yAak]

Confirmed issue was with using HDMI, reducing the Refresh Rate to 30hz.

Uncertain if it's a crappy HDMI cable (turns out monitor came with a DisplayPort cable, not an HDMI cable) or an issue with the USB-C hub's HDMI handling.

Using the monitor's DisplayPort cable to a USB-C adapter brings it to 60hz, resolves all lag issues.

 

[bclx99]

I can confirm, Display Port to USB-C works fine with 60 Hz! If I found that post earlier I would avoid many tries and errors. 😅