MacBook Pro M4 Multiple Display Issue

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SplitSeed Author

Level 1

4 points

MacBook Pro M4 Multiple Display Issue

Hi, I have searched around and have not found a solution to the following problem:

Current setup:

MacBook Pro M4 14in (Nov 2024)

x2 Alienware 32 4K QD-OLED Gaming Monitor - AW3225QF

x2 USB C to DisplayPort 1.4 Cable

I am unable to get both monitors connected at the same time, even if one is using HDMI and the other USB C. I'm assuming the issue is that the monitors max resolution and refresh rates exceed the supported external displays of the mac, however even when the display is set to within the supported specs the second monitor does not appear. Using the Detect Displays does nothing in this case either.

Here are the support specs for the MacBook from this source:

M4 Pro

Simultaneously supports full native resolution on the built-in display at 1 billion colors and:

Up to two external displays with up to 6K resolution at 60Hz over Thunderbolt, or one external display with up to 6K resolution at 60Hz over Thunderbolt and one external display with up to 4K resolution at 144Hz over HDMI
One external display supported at 8K resolution at 60Hz or one external display at 4K resolution at 240Hz over HDMI

Thunderbolt 4 digital video output

Support for native DisplayPort 1.4 output over USB-C

Thunderbolt 5 digital video output

Support for native DisplayPort 2.1 output over USB-C

HDMI digital video output

Support for one display with up to 8K resolution at 60Hz or 4K resolution at 240Hz

The monitors I am attempting to connect support resolutions up to 3840 x 2160 at 240 Hz however can be set lower within the Display settings on the MacBook.

In some miracle, at one point I did trick the MacBook to connect to both external monitors at a resolution of 3840 x 2160 at 120 Hz however I have not been able to replicate it. It was a combination of swapping a lower resolution monitor connected via HDMI and back and forth with the other monitors.

I will also note, even when connected via USB-C to DisplayPort, the Display settings on the MacBook allow me to set the resolution to 3840 x 2160 at 240 Hz, interesting!

I am hoping there is a solution to utilize both these monitors (knowing it will be at a lower refresh rate), thank you for your help in advance!

MacBook Pro 14″

Posted on Jun 13, 2025 8:47 PM

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Answer 1

SplitSeed Author

Level 1

4 points

Jun 14, 2025 11:31 AM in response to Grant Bennet-Alder

Hi Grant Bennet-Alder,

Thank you for all the great information! I do understand that I will not be able to max of the specs of the monitors, which I am perfectly ok with and knew from the beginning. My confusion comes from the fact the monitors support lower specs that the MacBook M4 Pro can output, yet the second monitor never shows up (except in 2 cases, one I can not replicate and one I can replicate).

Currently to get both monitors to show, I have to do the following:

Make sure all monitors are disconnected
Connect a low res monitor via HDMI port on the MacBook
Connect Alienware monitor via USB-C to Display Port (at this point 2 external monitors are showing)
Disconnect low res monitor from the HDMI port and connect the second Alienware monitor via HDMI Port
Now both displays are showing and usable

I've attached a few photos to show, we can get both displays connected with 3840 x 2160, 120 Hz and HDR enabled. Based on the stream info from the monitors themselves, the one connected via DP is using DSC, so the MacBook seems to support it. However, according to their supported specs for my MacBook, this should not be possible?

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Answer 2

Jun 14, 2025 7:33 AM in response to SplitSeed

That display appears to be a 4K display with 10 bits/color (HDR) capability.

Display connectivity includes:

2x HDMI 2.1 capable of 4K at 240 with HDR=ON, PROVIDED you are using a certified ULTRA HDMI cable

1x DisplayPort 1.4, capable of 4K at 240 Hz, BUT there are some issues:

Running at 10 bits/color takes a bit more bandwidth than 8 bits/color (HDR=OFF).

HDMI case:

Modern Apple-silicon Macs allow the HDMI port to run data rates high enough to obtain 144 Hz at 10 bits/color on a DIRECT connection (NO adapters). At 8 bits/color, up to 240 Hz refresh rates can be supported. You must be using ULTRA cables in every case..

DisplayPort cases:

When converting via USB-C adapter, there is not enough bandwidth on the USB cable to support any higher than 60 Hz refresh at 10 Bits/color HDR=ON; at 8 bits/color, up to 75 Hz can be supplied with data adequately to not drop out.

If you were using a Thunderbolt-to DisplayPort adapter (generally only available in a self-Powered Dock) those numbers improve to 144 Hz with a modest color compromise at 10 bits/color, and 144 with no compromises for 8 bits/color.

IF you MUST have HDR AND very high refresh rates, there are ways to get that much bandwidth by connecting two cables to each display.

NB>> if that is all "word salad" to you, please ask for clarification.

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Answer 3

TheLittles

Level 10

206,451 points

Jun 13, 2025 9:30 PM in response to SplitSeed

"MacBook Pro M4 Multiple Display Issue: [...]In some miracle, at one point I did trick the MacBook to connect to both external monitors at a resolution of 3840 x 2160 at 120 Hz however I have not been able to replicate it. It was a combination of swapping a lower resolution monitor connected via HDMI and back and forth with the other monitors.[...]"

-------

Getting Multiple Monitors:

A. Boot in Safe Mode:

Go Here: Start Up your Mac in Safe Mode - Apple Support

In Safe Mode, login item are set aside, and caches can be fixed.

B. Disconnect All Items:

Power off your Mac, and then disconnect all hardware from it. Then boot up, once more.

Based on personal experience...

C. Getting 3 External Displays:

The J5 USB-C Dual HDMI Docking Station allows for more than two extra monitors. How so? Well, plug in a display projector the Mac using the USB-C Digital AV Multiport Adapter and then plug the J5 hub with 2 HDMI displays (one 4K), and then you'll have 3 external screens. Two will be replicated, and one extended or mirrored.

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Answer 4

Jun 14, 2025 7:57 AM in response to Grant Bennet-Alder

I made a modest error above.

Both that Display and the MacBook Pro M4 support HDMI 2.1 standard.

The display specs are slightly ambiguous, but the HDMI standard is NOT.

the HDMI standard supports 240 Hz at 8 bits/color

At 10 bits/color, there is not enough bandwidth to support any higher than 144 Hz refresh, unless Display Stream Compression (DSC) is supported on BOTH devices. The Display supports DSC, but I am not certain the Mac supports DSC.

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Answer 5

SplitSeed Author

Level 1

4 points

Jun 14, 2025 11:00 AM in response to TheLittles

Hi TheLittles,

Thank you for your reply, here were the results:

A. Booting into Safe Mode did not help connect/detect the second monitor unfortunately.

B. Disconnecting, shutting down and rebooting did not help resolve connectivity issue either.

C. I do have a Dock as well, specifically CalDigit Element 5, although a dock should not be necessary to connect 2 external displays and the one I currently have does not have specific ports for monitors. I can see how that solution could potentially work. I also have x2 CalDigit USB-C to HDMI 2.1 8K Adapter Dongle however these do not seem to resolve any issues either, no matter the configuration.

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MacBook Pro M4 Multiple Display Issue

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