Why do the macOS resolutions on Big Sur render to the double which has been set up on 4K monitors?

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Why do the macOS resolutions on Big Sur render to the double which has been set up on 4K monitors?

Hi, I have been reading in several posts over the internet about the following issue I have with +4k resolutions on external monitors without having a concrete answer:

Either connecting the MacBook Pro using an HDMI or using a USB C DisplayPort I can notice that the resolution is always double what the UI reports, see the following image:

When I work with the maximum resolution for HDMI/DisplayPort the MacBook Pro becomes extremely slow, the performance is really bad, the fans are very noisy and the RAM is decreasing less than 1GB free.

The workaround I've found on the internet is decreasing the resolution, e.g: 2560x720, but this resolution is not optimal for my external monitor.

The same monitor connected to a Windows machine is running without any kind of issues.

My questions are:

Why does the MacOS always render to the double resolution which has been set up?

There is a way to avoid rendering to the double resolution which has been set up?

I have to comment that I cannot update to the latest OS distribution (at this moment) which is "macOS Monterrey" since the MacBook Pro is controlled by my work organization.

Any thoughts/ideas/workarounds will be very welcome here :)

Below you can find my technical specifications

Resolutions connecting the USB-C DisplayPort cable:

3840x1080
3360x945
3200x900
3200x900 (low resolution)
3008x846
3008x846 (low resolution)
2560x720
2560x720 (low resolution)
2304x648
2304x648 (low resolution)

Available refresh rate connecting the USB-C DisplayPort cable:

144 Hertz
120 Hertz
99.88 Hertz
59.88 Hertz

My Hardware:

macOS Big Sur

Version 11.6.3 (20G415)

MacBook Pro (16-inch, 2019)

Processor 2.6 GHz 6-Core Intel Core i7

Memory 16 GB 2667 MHz DDR4

Graphics AMD Radeon Pro 5300M 4 GB

Intel UHD Graphics 630 1536 MB

External Monitor:

Monitor name: 49" Super Ultra-Wide Monitor con Metal Quantum dot

Screen size: 48.9 Inch

Aspect relation: 32:9

Resolution: 3840x1080

Refresh rate: 144Hz

DisplayPort 1EA

HDMI 2EA

Mini DisplayPort 1EA

URL: https://www.samsung.com/mx/monitors/gaming/qled-gaming-monitor-with-32-9-super-ultra-wide-screen-49-inch-lc49hg90dmlxzx/

Cables:

USB C a DisplayPort Cable (4K@60Hz) CHOETECH,USB 3.1 Tipo C a DP Cable 1.2m (Thunderbolt 3)

MacBook Pro with Touch Bar

Posted on Feb 10, 2022 7:35 AM

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Answer 1

destiny241

Community Specialist

Feb 11, 2022 10:09 AM in response to shaveax

Welcome Shaveax,

Thank you for using Apple Support Communities. Based on your post, you have issues with your Mac running slow due to the high resolution on your external monitor.

We would disconnect all other accessories from the Mac and test it further.

It was hard to determine in your post, but are you using an Apple adapter to connect them: Connect a display to your Mac

You can also use: If your external display isn't detected or appears blurry on your Mac

If your Mac runs slowly

Have you had a chance to check for any firmware updates for this monitor through Samsung? The link wasn't in English, so it was hard to determine if there were any available on their website.

Let us know if this helps out, take care.

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