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KainsTorment Author

Level 1

19 points

Help I've got a issue with Dual Monitors on my 2023 Mac Pro M2 Ultra

I have this Mac and Monitors…

2023 Mac Pro

Apple M2 Ultra with 24-core CPU, 60-core GPU, 32‑core Neural Engine

64GB unified memory

Main Mac Storage 8TB SSD

With Two Separate PCIe Cards Storage 24TB SSD for Movies & Video (24TB per PCIe Card, so 48TB in all)

I’m running macOS Sequoia - Version 15.0.1

My Main Monitor: ASUS ROG Swift PG43UQ

(ROG Swift PG43UQ DSC Gaming Monitor — 43-inch 4K UHD (3840 x 2160), 144Hz,

G-SYNC Compatible, DSC, DisplayHDR™ 1000, DCI-P3 90%, Adaptive Sync, Shadow Boost)

https://www.amazon.co.uk/ASUS-Swift-PG43UQ-Gaming-Monitor/dp/B083QYQQ5Y/ref=cm_cr_arp_d_product_top?ie=UTF8

My Secondary Monitor: Sony BRAVIA XR XR-55A80L 55 Inch OLED 4K Smart TV

https://www.amazon.co.uk/Sony-XR-55A80L-Perfect-PlayStation5-Surface/dp/B0BX449WWF

Now before my 2019 Mac Pro strangely died and got replaced with my 2023 Mac Pro M2 Ultra I never had any issues with having Dual Monitors. After a few months of having my awesome 2023 Mac Pro M2 Ultra I had a issue where my Secondary Monitor would flicker on and of so I naturally I assumed it was a loose cable connection or a faulty HDMI etc. So when I realised it wasn't a loose connection I bought a new HDMI and no luck so bought a few more think it was a few faulty HDMI's but no, however the issue slowed down it my Secondary Monitor hardly went off but 2 Operating Systems later the problem gets worse. I often leave my Mac on over night as I often have work in process etc. but I turn off both screens but in the morning sometimes my Mac wont see my Secondary Monitor / TV, at the time I had a odd fix where i turned off and on the HDR setting on the Mac. However that trick stopped working and whenever my Mac doesn't recognise my Secondary Monitor the only way my Mac can see it is if I restart it.

My mate once told me its a common issue so is there a fix to this annoying problem. I've had Dual Monitors on most of my Macs but I've never had this issue so I hope you can help me.

Mac Pro, 15.0

Posted on Oct 18, 2024 11:51 AM

30 replies

Oct 20, 2024 8:28 AM in response to Grant Bennet-Alder

...and now for something completely different.

You could connect TWO adapter cables to your PIcture-in-Picture capable display, and each HALF display Left/Right could easily run at more modest speeds on its own cable. In the Mac, you set it up as two displays, then ARRANGE them adjacent Left/Right. in the Display, you use Picture-By-Picture (cousin of Picture-in-Picture) to place the two halves back in their proper orientation.

Readers report this works very nicely in Macs.

Apple does not recommend using HDMI adapters, especially at highest data rates, so the recommendation would be to use two ThunderBolt-to-DisplayPort adapter cables. Since each would be driving a 'very tall' 2K display, the restrictions are substantially reduced. the data rates for DisplayPort would drop to HBR2 speeds of about 17.28 G bits/sec for each of two cables, assuming 10 bits/pixel HDR.

KainsTorment Author

Level 1

19 points

Oct 20, 2024 7:23 PM in response to Grant Bennet-Alder

Thank you for all your patience Grant you must groan when you see a question from me lol.

I'm from the United Kingdom so it might be a UK issue but I've just looked on the UK Amazon Store for what you said ie "DisplayPort adapter/cable limited to 1 meter length, that can support 4K at 96Hz. The date rate HBR3, a very fast 25.92 G bits/sec"

I might be being really dim here and sorry if I am but. First I cant see any "DisplayPort adapter/cable" I assume a adapter means a small thing you plug the DisplayPort into then plug the adapter into the Mac? I'm not seeing any adapters like that and a few months ago someone once told me that cable adapters were a very bad idea as they over heat so I stopped using them. It was probably you who told me lol.

Secondly when I looked on UK Amazon Store for "USB-C/Thunderbolt 4 to DisplayPort adapter/cable 1 meter. support 4K at 96Hz. Data rate HBR3, 25.92 G bits/sec" couldn't see anything as low as 96Hz. 25.92 G bits/sec for some reason. But I did find this but I suddenly saw it was no good as it didn't have the G bit/sec thing

So I found this one its not 96Hz. and its not 25.92 G bit/sec but the lowest is pretty near though ie 4K@144Hz/120Hz ie 120Hz & 32.4Gbps. I cant find anything that exactly matches the stats you said though. Also I'm ignoring any cables that dont say HDR in the title.

Lastly quick question about my Sony TV. I know you said HDMI 2.0 but I suddenly thought is "HDMI 2.0b" slightly better?

[Edited by Moderator]

Oct 20, 2024 6:20 PM in response to KainsTorment

<< cable adapters were a very bad idea as they over heat. >>

There are words musing from that you wrote.

cable adapters TO HDMI were a very bad idea as they over heat.

(and that is the main reason Apple does not recommend them. The other is that HDMI is so confusing, and there are no bright lines or nomenclature changes when the technology and the requirements change.)

Oct 20, 2024 6:44 PM in response to Grant Bennet-Alder

the numbers I wrote in the descriptions are PRACTICAL speeds, and are not Marketing speeds. I added those numbers for YOU -- to illustrate how fast those data rates get in comparison to a USB-3 SuperSpeed+ at 10 G bits/sec or a ThunderBolt-3 at nominal 40 G bits/sec maximum, somewhat slower in practice.

The marketing numbers, if any are shown at all, are always quoted for 8 bits/pixel displays, and are rather different from what you seek, except for monoprice, who seem to have very good grasp on exactly what they are selling, where many others do not.

You need DisplayPort 1.3 or higher, which will run at HBR3 speeds, which is indeed the number I tossed out, 25.92 G bits/sec, but no one ever quotes that on goods for sale. This is faster than ANY USB ports can support, and it requires the cable to be plugged into a genuine ThunderBolt port. The right cable will probably say for 4K, at 120 or better, but this is based on 8 bits/pixel data rates.

The DisplsyPort adapter/cables you quoted are MORE capable than needed. If they are too expensive, look for cheaper Ones.

KainsTorment Author

Level 1

19 points

Oct 21, 2024 4:42 AM in response to Grant Bennet-Alder

I know you mean well but I'm getting lost in so much information so please can you look on the Amazon UK Store and just link me a suitable 1m USB-C to DisplayPort please. Also can you please link me a suitable 3m HDMI please so I can just buy it. why I ask is because I often buy the wrong one, and If you link them I know I'm definitely buying the right cables. Thanks Kain

KainsTorment Author

Level 1

19 points

Oct 21, 2024 3:07 PM in response to Grant Bennet-Alder

So if I bought this USB-C to DisplayPort 1.4 https://tinyurl.com/32ymhnhd for my ASUS to my Mac, would this fix the flicking issue?

And if I bought this HDMI 2.0 https://tinyurl.com/4d875ere for my Sony Bravia TV to my Mac would this fix the flicking issue?

Can you let me know if I picked the wrong thing before i buy please? thanks

KainsTorment Author

Level 1

19 points

Oct 24, 2024 5:30 AM in response to KainsTorment

Hi Grant Bennet-Alder thanks those to cables seem to be working ie no flickering so thank you.

However I've got a new issue on my main screen the 43" ASUS. its finally in 144Hz however in HDR mode games or the desktop or anything red looks washed out even on my favourite Display Colour Profile "sRBG IEC1966-2.1" I first looked at the utilities app ColorSync Utility thinking I could adjust contrast etc but it looked beyond me lol. Then I found colour Contrast in Accessibility but it wasn't what I needed. I then turned HDR Mode off and everything looked normal... When I had HMDI on my main screen colours looked fine even with HDR Mode on but if DisplayPorts are better why do they make HDR look awful and pale?

I turned off HDR but is there a app or fix you adjust HDR on Mac to fix HDR how you want not dull?

I'm a movie freak originally bought the ASUS for HDR for movies and games

Oct 24, 2024 3:02 PM in response to KainsTorment

did you select the Color Profile specified for your display?

I use an Apple Cinema HD Display and the profile that appears at the top of the list, and presumably gives the "best" color is called "Apple Cinema HD Display"

Oct 25, 2024 11:46 AM in response to KainsTorment

<< Mac not recognising my second screen>>

The Mac does not rely on windows-like side-loaded "Drivers" which are actually packages of resolutions and settings for a specific display. Instead, it goes straight to the immutable source -- it asks the display itself.

To get a Mac display to become active, you need the Mac to query the display, and the display to answer with its name and capabilities. Otherwise, the display will not be shown as present, and no data will be sent to the display. "No signal detected" is generated by the DISPLAY, not by the Mac.

This query is only sent at certain times:

• at startup

• at wake from sleep — so momentarily sleeping and waking your Mac may work

• at insertion of the Mac-end of the display-cable, provided everything on that cable is ready-to-go

• hold the Option key while you click on the (Detect Display) button that will appear in Displays preferences (from another display)

KainsTorment Author

Level 1

19 points

Oct 25, 2024 1:00 PM in response to Grant Bennet-Alder

most of that went over by head but I never put my Mac in Sleep mode as I'm always downloading.I hardly ever turn my Mac off too so it should see the screen. Whenever it doesn't see the second screen I look in Displays and its not seeing it so I couldn't Option click on it anyway.

Also my new DisplayPort cable has definitely changed the colours annoyingly compared to HMDI I wasn't expecting that

Oct 21, 2024 3:16 PM in response to KainsTorment

Yes, those would both work for the purposes you described.

KainsTorment Author

Level 1

19 points

Oct 21, 2024 3:25 PM in response to Grant Bennet-Alder

Thank you so much i've just bought them.

KainsTorment Author

Level 1

19 points

Oct 24, 2024 1:09 PM in response to Grant Bennet-Alder

As far as I can tell the Calibrator does nothing for colour its only brightness and whites. ie warm or cool. i'm after to adjust the contrast or colour

KainsTorment Author

Level 1

19 points

Oct 26, 2024 8:04 AM in response to Grant Bennet-Alder

ah that'll be a problem because in the Displays preferences whenever my Mac doesn't recognise my second screen I cant hold option click on it as only my ASUS shows up in the Displays preferences

Oct 26, 2024 10:32 AM in response to KainsTorment

Then you will have to use one of the others listed.

Help I've got a issue with Dual Monitors on my 2023 Mac Pro M2 Ultra