4K Monitor Only Displaying 2560x1440p

I recently bought a new monitor (Acer Predator XB323QK) which has USB-C Power Delivery for using with my 2019 Macbook Pro 16". Im using an Apple Thunderbolt 3 Cable between the 2 devices. When first booting up and trying it out, it worked great and showed the monitor in full resolution as it should. I chose the middle option when choosing the scaling which stated that it would slow performance but i didn't mind.


However upon the second time booting up my system and each 10-20 times after, the monitor is now only showing the option on 2560x1440p and doesn't actually give me the scaling option where you can choose the text size and it tells you that it will effect the performance. It now only shows me the actual resolutions I can choose from and 2560x1440p is the highest and it is really obviously dropped.


Im a photo editor and its is very obvious and hindering my work.


Ive tried unplugging and plugging back and but it will not go back to what it was like when i first used it.


Thanks.

MacBook Pro (2017 – 2020)

Posted on Jul 31, 2023 6:53 AM

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17 replies

Jul 31, 2023 7:24 AM in response to MattLens

Okay, MattLens, since you don’t have an m1/m2 Mac ( Apple silicon) you can do something, try this first :

reset smc/pmu and zap pram 3-4 times on startup per this link : https://www.macworld.com/article/224955/how-to-reset-a-macs-nvram-pram-and-smc.html then see what’s going on..I presume you know that holding down the “option” key while going into system prefs> display/ monitor will get you the scaled for display choice every time…


John b

Jul 31, 2023 8:01 AM in response to MattLens

to use that 4K display on a USB-C cable, the cable length must be limited to under 1 meter in total length.


Otherwise, errors may be detected by a Modern Mac running recent macOS, and the resolution will be automatically reduced. You Might get higher resolution if you select a lower refresh rate.


For genuine ThunderBolt displays (this is not one), maximum cable length is 0.8 meters for Apple cables, 0.5 meters for brand-X cables.

Jul 31, 2023 8:38 AM in response to Grant Bennet-Alder

Thanks for your help here Grant. The cable length is 0.8m and is an official Apple cable so this shouldn't be an issue here. Ive tried reducing to the only other refresh rate option which is 59.88hz but this does not make a difference. The strange thing here is that when I first tried everything it was fine at 4k and 60hz. But those options seem to have just disappeared.

Jul 31, 2023 12:33 PM in response to MattLens

You left out the key issue that is causing you grief.


When you chose to Mirror Displays, a 'compromise' resolution is computed, which is expected to be attainable by both displays, and BOTH are run from a single display-generator in perfect unison.



the two blue Icons for two displays are nearly co-incident, indicating Mirrored.



--------

if you want to be able to reach the top resolutions, the displays must be independent,

Extended Desktop:




Aug 1, 2023 9:09 AM in response to MattLens

I posted older versions because they 'talk to me' in a very Visceral way, something the changes in Ventura do Not accomplish.


Your latest screenshot is different from the ones you posted earlier (which showed the same picture on each display).


What happens when you select "extend displays" off that drop-down menu featured prominently in your screenshot?

4K Monitor Only Displaying 2560x1440p

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