M1 MacBook with External Monitor - Refresh Rate / Stability Issues.

[rkieru]

I have a 2020 M1 MacBook Pro running macOS 12.0.1 and I have it connected to a Dell S2721QS 27" Monitor via a DP to USBC cable that is rated for 4K @ 60Hz or 2K at 144Hz.

When I have my MacBook Pro lid open there are no issues. I can run the monitor set to either a variable rate (40-60Hz) or force it to 60Hz without an issue. However, if I close the lid to my MacBook Pro these settings immediately cause my external monitor to shut itself off periodically (about every 7 - 10 seconds).

The only resolution I have found is to reduce the refresh rate to 30Hz, well below what the monitor, cable, and MacBook should be capable of running, and a rate that makes things like mouse movement feel rougher.

Has anyone encountered this issue and found a resolution?

I'm not sure if any of this matters but here are links to the exact cable and Dell Monitor that I have.

Warrky USB C to DisplayPort Cable 8K 60Hz [Stable Gold-Plated Plug, Metal Case] 4K 240Hz, 2K 360Hz Type-C to Display Port Cord, Thunderbolt 3/4 Compatible with MacBook Pro/Air, iPhone 15, iPad, Galaxy

www.amazon.com

Dell S2721QS 27 Inch 4K UHD (3840 x 2160) IPS Ultra-Thin Bezel Monitor, AMD FreeSync (HDMI, DisplayPort), VESA Certified, Silver

The Dell S2721QS Monitor provides stunning visuals. It has a 27-inch 4K UHD IPS display that provides breathtaking clarity and vibrant colors. The ultra-thin bezel design provides an immersive viewing experience. Enjoy tear-free gameplay and smooth visuals with AMD FreeSync technology. With HDMI ...

www.amazon.com

I also have an Anker USB C Hub, though the Monitor is not plugged in to this device.

Anker USB C Hub, 341 USB-C Hub (7-in-1) with 4K HDMI, 100W Power Delivery, USB-C and 2 USB-A 5 Gbps Data Ports, microSD and SD Card Reader, for MacBook Air, MacBook Pro, XPS, and More

A8346

www.amazon.com

 

[tbaer]

I have the same issue. Using a hdmi adapter now to work around it.

Known issue:

Flickering or Blanking Video Issue with Dell S2721Q, S2721QS, and S3221QS Monitors when Connected to a M1 MacBook or Mini via USB-C to DP Adapter | Dell US

 

[The.Walrus]

Hi. Same issue here, on exact same gear (2020 M1 MBP and Dell S2721QS with DP USB-C cable rated 4k 60hz). The only "fix" I've found is to toggle the System Prefs > Display from "Variable 40-60hz" to "60hz" back and forth until the flickering eventually stops. It's annoying af.

 

[aaronlee9303]

Hey guys, I know this post is kinda old, but I wanted to share some information with you guys. I was suffering from the issue where the default refresh rate kept becoming variable, but finally I think I found the key by using EasyRes application on App Store, which is free. I don't know why, but ever since I set the resolution and the refresh rate by the app, it keeps recovering the refresh rate that I set before even if I terminate a game which changes the resolution. Try to use EasyRes guys.

 

[mtcnbzks]

Hey guys, I know this post is kinda old, but I wanted to share some information with you guys. I was suffering from the issue where the default refresh rate kept becoming variable, but finally I think I found the key by using EasyRes application on App Store, which is free. I don't know why, but ever since I set the resolution and the refresh rate by the app, it keeps recovering the refresh rate that I set before even if I terminate a game which changes the resolution. Try to use EasyRes guys.

I just opened this account for say thank you. Now I can use my monitor 165HZ (M1 Macbook (2020)) thanks to your app suggestion.