Level 1

61 points

Mac Studio M1 Ultra External Monitor Flickering

So tired of this....

Before anyone suggests that I read this or check that or change cable.... That has all been tried to death.

Apple M1 Macs have an issue with external monitor flickering. Period. Every OS update I wait in the hope that it gets fixed. Nope... Just did the update today and it flickered within about 2 hours.

In my situation I have 2 external BenQ monitors, 1 is 4k 32" PD3205U and the other (flipped sideways) is a 27" 1080p PD275Q.

The 32" is connected via a good HDMI cable and the 27" via a thunderbolt cable. Yes, I have tried MANY different cables)

I have a couple of external SSD enclosures in a Raid0 and another external SSD for backups. USB-C to DAC, and one or two other connections. Whether they are connected or not does not affect this.

Periodically, the 32" starts to flicker, mildly at first, then it may increase or stop entirely.

When you look closely at the pixels while this is happening you can see that alternate vertical rows of pixels are shifting. Reminds of old CRT monitors. It can flicker quite dramatically sometimes.

From what I can tell, this is NOT a 3rd Party hardware issue (cable or monitor). The issue usually happens when I am working in Photoshop or Illustrator and I am in the finder which usually consists of 2-3 large windows. The flickering comes out of nowhere. If I tab back to Photoshop the flickering may stop. Or, may not be as bad. Cycle through various apps and it usually changes. To me, the Finder is affecting this, or some part of the OS that is translating to the display.

BenQ have a page dedicated to the issue: https://www.benq.com/en-us/knowledge-center/knowledge/how-to-fix-mac-m1-m2-external-monitor-flicker.html

None of their suggestions nor anyone else have helped. There are tons of posts everywhere from Reddit to Macrumours to here that all raise the same issue (for the most part). Still.... no fix or no acknowledgement from Apple. Everyone says to change the cable or whatnot but it seems the issue persists for most of us.

I've been an avid Mac user since 1990 so I have an idea of how to troubleshoot these issues.

If anyone can give me any insight on how to resolve this I would be eternally grateful.

The odd thing is it tends to happen when I get very busy! Maybe it's picking up on my karma....

Mac Studio (2022)

Posted on Mar 26, 2024 11:46 AM

Top-ranking reply

Grif_ Author

Level 1

61 points

Posted on Oct 18, 2024 12:55 AM

Hi Folks,

OK so I have an update and it's quite interesting.

A RESULT! NO FLICKER!

1st: The Apple Thunderbolt 4 Pro 1.8M cable (Active) seems to have fixed the issue. It's a €149 cable but I have not had one flicker since I installed it on Spet 12.

https://www.apple.com/es/shop/product/MW5J3ZM/A/cable-thunderbolt-4-pro-usb%E2%80%91c-de-18-m

2nd: BenQ support informed me that there is a hardware update that they can perform on the monitor that they say will address this problem. They have provided me with a shipping slip for the monitor and stated there would be no charge for the repair.

I have yet to ship my monitor off as I'm extremely busy and can't do without it for 1-2 weeks. If I can find a temp monitor I'll do it but for now I'm just happy there's no flickering.

That said. I'm still at a loss to why this is happening. I'm also convinced this is ultiamtely an issue with the Apple Silicon. How a specifc browser can trigger a random flicker response is beyond me.

I'm sure somenone a lot more technical than me can explain this and also maybe explain why an Active Cable solves the issue.

So happy, no flicker! (For now)

Hopefully this helps someone.

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44 replies

Grif_ Author

Level 1

61 points

Sep 10, 2024 4:15 AM in response to Grif_

Another day another flicker!!

What's setting it off today is a Google Chrome window with mostly black content.

This is driving me nuts and I'm not sure what to do at this point. I'd get rid of my BenQ 32" and get another make if I thought it would resolve the issue but most say it's not BenQ related.

Grif_ Author

Level 1

61 points

Sep 10, 2024 8:04 AM in response to BDAqua

yea, I mentioned a couple previously

.5M HDMI Ultra High Speed - Ubluker 10k 8k 4k HDMI 2.1 Cable 0.5M, Certified Ultra High Speed HDMI Cable 4K 120Hz 144Hz 8K60Hz 48Gbps ARC eARC Dolby Atmos HDCP2.3 Compatible Mac RTX4090 PC HDTV PS5 Xbox https://www.amazon.es/dp/B09ZRPJZDL?ref=ppx_yo2ov_dt_b_product_details&th=1
.3M Thunderbolt 4 - Angusplay Thunderbolt 4 USB C Cable 0.3M, USB4 40Gbps Cable, 100W 8K 60Hz Video TB4 Cable Compatible with Thunderbolt 4/3, USB4/3, Type C, for iPhone 15/15 Pro Max Mac MacBook Pro, eGPU External SSD https://www.amazon.es/dp/B0CNGS6576?ref=ppx_yo2ov_dt_b_product_details&th=1

Along with a bunch of others I have in a drawer. .3M TB4 cable is via rear port, any port, same results.

Oct 18, 2024 7:07 AM in response to Grif_

<< I'm still at a loss to why this is happening. >>

1) based on what you said, BenQ said there was a hardware design problem in the display, and is willing to repair it for free.

2) based on what Users said, a genuine ThunderBolt cable must be shorter than 0.8 meter for Apple super-engineered cable, or 0.5 meter for brand-X cables. Otherwise, electrical signal degradation in too-long cables make the signal deteriorate so badly that it is unusable.

You worked around that by using a cable that avoids the electrical signal losses by converting to fiber-optic and back, for a much higher price. It's good for Readers to know that the Active Fiber Optic cables work at extended distances. So we all learned something.

Grif_ Author

Level 1

61 points

Oct 18, 2024 8:59 AM in response to Grant Bennet-Alder

Hi Grant. I did try .5M TB4 cables. Same issue.

This also did not happen on any other Mac I have, MBP 2019 and a MacPro 2019, both intel. They work fine with the other cables I have. I guess Apple Silicon seems to treat this differently. Judging by similar posts in other M1/2 related discussions.

It was also a massive pita to troubleshoot. If it is the case that Apple silicon Macs require very specific cables to work with some 4k monitors this should be made clear. Somewhere. Either the monitor manufacturers or Apple. It also does not seem to be consistent. Some folks have the issue, some don't.

In my case, lesson learned I guess. :-)

Thanks for all your input.

Apr 17, 2024 2:10 PM in response to shtl2

do you have the appropriate cables to support this display at high resolution?

what display? what resolution?

what cables, adapters and docks are in use?

Grif_ Author

Level 1

61 points

Apr 23, 2024 7:23 AM in response to Grant Bennet-Alder

Hi Grant, thanks again for your time.

I've always had the monitor on a fixed refresh rate of 60 Hertz.

BDAqua

Level 10

250,253 points

Aug 31, 2024 7:26 AM in response to beatsbythehuman

What length cables?

BDAqua

Level 10

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Aug 31, 2024 10:32 AM in response to beatsbythehuman

6' ??? Are they active cables?

BDAqua

Level 10

250,253 points

Aug 31, 2024 11:01 AM in response to beatsbythehuman

OK, sorry I missed or didn't understand. I can be of no help, best of luck.:)

BDAqua

Level 10

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Aug 31, 2024 11:13 AM in response to Grant Bennet-Alder

Thanks Grant, I think that was where I was going before I got lost.:)

BDAqua

Level 10

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Sep 10, 2024 7:53 AM in response to Grif_

I haven't read all three pages, but has the cable been mentioned, it's length & port?

Grif_ Author

Level 1

61 points

Sep 10, 2024 8:26 AM in response to Grif_

OK, so I'm gonna try an Active Apple cable.

what's the bet I get the same results?

BDAqua

Level 10

250,253 points

Sep 10, 2024 9:01 AM in response to Grif_

Your Amazon links both do this...

BDAqua

Level 10

250,253 points

Sep 11, 2024 6:33 AM in response to Grif_

Thanks... so those do not fix the problem?

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Mac Studio M1 Ultra External Monitor Flickering