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Connecting 2x Dell U4025QW 5K @ 120hz to M4 Max

L

Lord_Stargazer

macrumors newbie
Original poster
Sep 6, 2025
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Dubai
My first post! Yay! Be gentle.

I looked everywhere and I am not finding any clear answers. Sad that Apple only publishes some sample resolutions. Dell is pretty common. I would have expected Dell to post compatibility lists for the most widely used computers and at the same time I would have expected Apple to post compatibility lists for the most widely used monitors. Somehow I expect that Dell should list the latest Apple devices and Apple to list, at least, the most high end monitors.

Does anyone here know? 2x Dell U4025QW 5K 120Hz Ultrawide paired with a MacBook Pro M4 Max (highest spec in terms of chip with 128GB memory).
 
Note that my current M4 Pro with 24GB memory is not able to do this, which is why I am crossing my fingers that the beast I am getting will be able to…. 🙂
 
I remember reading about M4 and issues with 5K2K displays… something about limited horizontal widths, which limit HiDPI (retina) resolutions. I recommend you continue researching before committing. You also may need a virtual display frame buffer solution like BetterDisplay for the 5K2K. Here is a link I bookmarked last spring -
github.com

M4 and 3840 x 1620 hidpi resolution on 5K2K ultrawides · waydabber BetterDisplay · Discussion #3812

Hi, It seems my only way to avoid sleep issue with virtual screen and mirroring is through your native/flexible scaling. I tried adding the custom resolution but I'm only given a lodpi option at 38...
github.com github.com
 
Thank you, Bigwaff. Much appreciated.

But there is absolutely zero issue with 1x Dell U4025QW with 5K at 120Hz, even with a M3 chip. I used that for over a year at my previous startup. Multiple users. All very happy.

The question specifically is when connecting 2 of these displays. Anyone with hands-on experience? Not read something somewhere, but actually tried and tested?

​

 
Did you try connecting the 2x Dell U4025QW to separate Thunderbolt ports of the M4 Pro?

M4 Pro supports 2 of these:
- 6K60 is 1280 MHz
- 4K144 is 1310 MHz

or M4 Pro supports 1 of these:
- 8K60 is 2070 MHz
- 4K240 is 2290 MHz

M4 Max supports:
- 4 of the former category
- or 2 of the former category and one of the latter category.
I'm not sure why it couldn't support 2 of the latter category since 2 of the former category is greater than 1 of the latter category in terms of total pixel clock?
But maybe it's easier to do multiple slow clocked displays than one fast clocked display.

5K2K120 is 1430 MHz so maybe it's in the latter category? In that case, it is unknown if two are supported on M4 Max because Apple doesn't list the real limitations (the resources of the hardware and how they can be split among displays).

Looks like M3 puts 5K2K120 in the former category and doesn't support the latter category. You can close the lid to output to a second external display but the possible displays are in a third even slower category:
- 5K60 is 930 MHz
- 4K100 900 MHz

M2 Pro and M3 Pro can connect two of the former category or one of the latter category.

etc.
https://support.apple.com/en-us/101571
 
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Thank you. I don’t fully understand the MHz limitations or logic, but that is a good pointer. I will read more about that. I only read the resolution and refresh ratio limitations, so far.

I just find it strange that there are no more extensive compatibility lists. Given the prices we pay, that should be a minimum.
 
If you commit, please post pictures and screenshots!

That sounds like an absolutely bonkers setup. Jealousy guaranteed ;-)

(Running a 2018 i7 MacMini with 2*4k, always contemplating getting a 3rd 4k diskplay...)

Is there a VESA-mount for this setup?
 
Last edited:
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IMG_6215.jpeg
 
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Confirmed.

The M4 Pro can only power 2x Dell U4025QW with 5K at 60Hz. The M4 Max can power 2x Dell U4025QW with 5K at 120Hz.

The image quality difference is substantial! I love this setup! 🙂

Very happy with my purchases. Now, the development fun can begin.
 
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Lord_Stargazer said:
Confirmed.

The M4 Pro can only power 2x Dell U4025QW with 5K at 60Hz. The M4 Max can power 2x Dell U4025QW with 5K at 120Hz.

The image quality difference is substantial! I love this setup! 🙂

Very happy with my purchases. Now, the development fun can begin.
Click to expand...

Are you using the stock USB-C cable? Running it through a USB hub? I currently have the U4021QW at 5K@60Hz and a new U4025QW still in the box as I can't get a clear answer from Dell on this!
 
I am using the Thunderbolt 4 cables supplied by Dell. The ones that came with the monitors. Work perfectly. I have my M4 Max connected to the main USB-C port of each monitor, the high-power port that is open by default. The other USB-C ports have orange silicon protectors in them.

This way, I get the full 5K at 120Hz signal plus power. I even have an Ethernet cable connected to my monitor and the connected Thunderbolt 4 cable carries that as well, providing 1 Gbps of internet speed, in my case.

Thunderbolt 4 is sufficient for data and power. I am happy.
 
Good to know! I'm trying to power the U4025QW at 120Hz PLUS a 4k@60Hz over one cable as my setup isn't really conducive to putting cables on left side... and I use the laptop screen and camera for video calls. Just bought myself an anker thunderbolt 5 that should arrive shortly. Hopefully that'll cut the mustard.
 
That I am not sure about. I have not heard about Apple devices supporting daisy-chaining, or connect monitors over hubs very well. I think you need separate cables for each monitor. That is what I have, in case that was not clear. Each monitor connected to one USB-C port individually.
 
I ordered the Dell UltraSharp 4K webcam. I used it before and the picture quality is stunning. I will use that with my setup.
 
Well, I have 2 ultra-wide, so I guess with my dual-ultra-wide I am in both camps? 🤣

To be fair, one ultra-wide was not enough for me, but two ultra-wide are a bit too much. I am waiting for another 5K from Dell with the same height and normal width that runs at 120Hz, and has the same eye comfort certification. That should then be perfect.

​

 
I'm currently running the 5k2k@60Hz with the 4K@60Hz via the Thunderbolt 4 Dock from Dell. Works great. The problem is Thunderbolt 4 doesn't have enough bandwidth to support 5k2k@120Hz via the hub (I tried). The U4026QW only has Thunderbolt 4 upstream, which will work if all I want is in one screen, but it doesn't seem to have sufficient bandwidth to connect other screens downstream like the Hub can.

@MRrainer - indeed, ultra-wide vs dual display vs single display is a very personal choice. Some of the best engineers I've worked with don't want more than a single 1080p display with full-screen tmux.
 
I got a Twelve South Book Arc today and my setup looks even better now! 🙂

Also, the better cooling will surely help.

By the way, nobody commented on the rubber duck. I guess not many developers here? 😉
 
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