Mac Studio M1 Ultra External Monitor Flickering

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Level 1

51 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

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Answer 1

Top-ranking reply

Grif_ Author

Level 1

51 points

Jul 4, 2024 2:13 PM in response to Grant Bennet-Alder

Hey Grant,

so BenQ are aware of the issue. There’s a link to their response on the OP. They suggested various steps which I’ve gone through a few times with no change. What’s interesting is they mention to change the “image pattern” that triggers the flickering. So they too know that displaying some sort of pattern causes the issue.

I had it hooked up to my MBP with no issues. It’s an Intel though.

I’ll have another look through the monitor settings but fairly sure I have it set for standard sRGB. No gaming settings that I can see

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Answer 2

Grif_ Author

Level 1

51 points

Sep 1, 2024 2:30 AM in response to Grif_

I had a vague flicker (ex pun) of hope when I saw the release notes of the last update to sonoma when they mention an issue with video

macOS Sonoma 14.6 Release Notes | Apple Developer Documentation

It had to do with video toolbox. It also wasn’t specifically about flickering either but I’ve seen Apple do this before. Fix one thing that also fixed another possibly related issue not mentioned.

Alas no. Flickering still happens. Mind you, it only happened once since the update so far.

I also mentioned in previous posts that it doesn’t happen to a lower resolution monitor. Only the 4k one. It also seems this is not a benq only issue either. It also seems that cables have no effect.

The video signal seems to collapse and go out of some sort of sync. As I’ve mentioned before this also seems to be display content related. A web page may cause it, control-tab to another app and it stops. But usually it grows worse. Mostly it happens when I’m in an Adobe app.

Being a Mac User since about 1991, my first Mac being a IIsi, this is the first time I’ve come across a hardware issue on desktop macs that is being ignored. Plenty of issues with various Mac laptops over the years like the display issues and keyboard issues but they usually get resolved by Apple. Usually with a replacement of some sort.

There just seems to be no acknowledgment of this issue whatsoever.

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Answer 3

Grif_ Author

Level 1

51 points

Oct 18, 2024 12:55 AM in response to Grif_

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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Answer 4

Grif_ Author

Level 1

51 points

Apr 23, 2024 3:42 AM in response to Grif_

Steps taken so far

Replaced cables

.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

Note, I already had several TB4 rated cables .5M but I thought I’d try a shorter one.

Peripherals

Thunderbolt/USB-C
Monitor Connections are direct to rear TB4 ports
2 x external NVMe SSD Drives TB3 (Striped)
1 x Samsung t5 SSD

USB-A

DAC

Tried the following

Restart Mac Studio - Flickering picks up where it left off
Disconnect Power to monitor - Flickering picks up where it left off
Create a new user - Flickering picks up where it left off
Change display resolution - No change to flickering
Change display Refresh Rate - No change to flickering
Toggle HDR (usually off) - no change to flickering
Night Shift - set to off
Display Pilot (BenQ) - ICC Sync on/off - no change
Changed HDMi cable to the .3M TB4 cable. - Flickering stopped - for now.

Observations

The flickering starts mildly and gets progressively worse, then… eventually just fades off.
If you look at the closeup the flickering seems to manifest as vertical lines

Let’s see how I get on with the TB4 cable

https://youtu.be/buOp33e97M8

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Answer 5

tkinson

Level 1

8 points

Jul 29, 2024 12:29 AM in response to Grif_

I'm having the same issue. Flickering interlace image over HDMI with a mac studio m2 max and a Dell S2721Q 4k monitor.

I've tried:

different HDMI cables (no change)
disable nightshift (no change)
disconnect and reconnect monitor (no change)
power cycle computer (no change).

It tends to happen late afternoon for me (so could be triggered by night shift starting).

After 10-15 mins it goes away.

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Answer 6

Jul 4, 2024 1:07 PM in response to Grif_

<< Only happens on the BenQ 32", the other monitor is fine. >>

do you have another video source to swap in to use the BenQ display with?

consider scanning the manual for "on-screen display" settings (internal to the display). Some users have found that internal display settings for gaming interfere with their spreadsheets, for example.

Consider contacting BenQ for Assistance.

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Answer 7

Aug 28, 2024 7:25 AM in response to Grif_

It really is very frustrating, I've got exactly the same monitor and have exactly the same issues. I'm coming to the point where I have no choice but to swap out the monitor because just as I am in the middle of something important it happens and it's so hard to look at the screen when it's flickering like that. If a reboot or something fixed it, then it would be at least bearable but it doesn't.

The real question is, what monitor do I even pick, I daren't rely on any reviews.

Does anyone have/know of a list of 'safe' monitors (32" 4k) that work well with the Mac Studio MAX that don't have any flickering?!

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Answer 8

Aug 28, 2024 9:05 AM in response to neiled_usa

did you see this line in the original posting?

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

If Benq thought for a moment this was a problem that Apple caused by deviating from standards, they would have blurted out what they had found.

Apple-silicon Macs are unique in that they have the memory bandwidth to be relentless in sending data to the display. Display-makers may have 'gotten away with' slower data transfers in the past, but now that the data appears at top speed, it is becoming a problem.

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Answer 9

Aug 31, 2024 11:08 AM in response to beatsbythehuman

To use a ThunderBolt to DisplayPort adapter/cable, the Thunderbolt/USB portion from the computer to the adapter electronics must be shorter than one meter. The cable from the adapter electronics to the display must also be shorter than one meter.

if the adapter electronics are in the distal (far from the computer) end, the total length of the adapter/cable is limited to one meter.

--------

If supporting a high-end display with a genuine Thunderbolt cable, that cable needs markings at both ends indicating it is a [tested and] certified Thunderbolt cable. The length of such a cable is limited to 0.8 Meters, maximum for highly engineered Apple brand cables, and 0.5 meters max for Brand-X cables. Such cables are not 'active' cables (with ThunderBolt repeaters in them), which cost in excess of US$200 each for modest lengths like two or three meters.

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Answer 10

Aug 31, 2024 11:34 AM in response to BDAqua

I am happy to help. I have been studying this stuff, and had the limits mostly in my memory and a quick look-up away. So adding them to this discussion was not much heavy lifting.

What swapping Different (unspecified) display cables does, is hedge against BROKEN cables. These days Broken cables are rarely the issue. It's mostly cables that are too long, too low spec, or not certified (so not likely good enough quality to pass a certification test.)

The rapid jump in external display resolution to 4K and beyond requires far more precision in the cables, because those data rates are ferocious! Cables that worked with Windows, or with older systems, or with lower-resolutions sometimes just don't make the cut.

Apple-silicon Macs have taken a HUGE step forward in computer architecture by increasing the bandwidth to RAM memory, by almost an order of magnitude. That allows even faster fetching of display data, and stuff that used to 'get by' at slightly slower speeds no longer 'gets by' without generating errors.

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Answer 11

Aug 31, 2024 4:11 PM in response to beatsbythehuman

To be used for high-end displays on a Mac, it also needs to be one meter or shorter.

Recent versions of MacOS are ready the status provided by the display. Any transmit errors cause the link to disconnect or reduce the relation. cable longer than one meter tend to use too mush signal attenuation, and that shows up as errors.

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Answer 12

Grif_ Author

Level 1

51 points

Sep 11, 2024 12:10 AM in response to BDAqua

Angusplay Cable Thunderbolt 4 USB C 0,5M, Cable USB4 40Gbps, 100W Vídeo 8K 60Hz Cable TB4 Compatible con Thunderbolt 4/3, USB4/3, Tipo C, para iPhone 15/15 Pro Max Mac MacBook Pro, SSD Externo eGPU

https://www.amazon.es/dp/B0CNGQR5X2

Ubluker 10K 8K 4K Cable HDMI 48Gbps 1M, Certificado Ultra Alta Velocidad HDMI® Cable 4K 240Hz 144Hz 8K60Hz 0.01ms HDR10+ ARC eARC HDCP2.3 Netflix Roku TV PC Monitor Proyector PS5 Xbox

https://www.amazon.es/dp/B08TGBLLXY

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Answer 13

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.

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Answer 14

Grif_ Author

Level 1

51 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.

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Answer 15

Apr 18, 2024 8:01 AM in response to shtl2

<<. Lowered the resolution to 2560x1440 so I can read texts. >>

the "approved method" to obtain readability of TEXT is to use settings for Scaled TEXT "looks like" (larger/smaller) in the displays preferences, NOT lower overall resolution. This scales ONLY TEXT being displayed, and leaves the graphics at full resolution so you can enjoy the resolution you paid for when displaying graphics.

...

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Mac Studio M1 Ultra External Monitor Flickering

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