M2 Max daisy chain dual extended displays using only one thunderbolt port

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M2 Max daisy chain dual extended displays using only one thunderbolt port

Hello,

i am having trouble connecting two extended displays in daisy chain using just one thunderbolt port.

monitors are two 4K dell u3223qe

i have one monitor connected with a thunderbolt 4 cable and the second monitor in daisy chain via display port from the 1st monitor.

The problem is that i just get the same image on both. The displays are mirrored and I want them to be extended.

My M2Max macbook only recognises the monitor which is connected , and it doesn’t recognized the second daisy chained monitor .

how can I get both monitors to work in extended mode using just one of my M2 Max thunderbolt ports?

MacBook Pro 16″, macOS 15.2

Posted on Jan 23, 2025 9:49 AM

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Answer 1

Top-ranking reply

Grant Bennet-Alder

Level 10

141,733 points

Jan 23, 2025 10:55 AM in response to PetrolMan

Dell 4K u3223qe appear to be a 4K display with 10 bits.color HDR

Interfaces

HDMI (HDCP 2.2)
DisplayPort 1.4
DisplayPort output
USB-C upstream/DisplayPort 1.4 Alt Mode with Power Delivery (power up to 90W, HDCP 2.2)
USB-C 3.2 Gen 2 upstream

check that list carefully. it is NOT a ThunderBolt-capable display.

its interface runs at only half the effective speed and provides half the bandwidth of a Thunderbolt interface. It has NO additional bandwidth for a second display, which is why the Mac does not support TWO displays on its ONE USB-C cable. Just using a Thunderbolt cable does not mean the display can accept real Thunderbolt data.

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Answer 2

Jan 23, 2025 11:29 AM in response to PetrolMan

You could connect the second display with a certified ULTRA spec HDMI cable and not use up a Thunderbolt port that way. Those cables are backward compatible.

At HDR data rates, it can clearly attain 50 Hz refresh rate. Higher may require some compromises in color or resolution.

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Answer 3

PetrolMan Author

Level 1

8 points

Jan 24, 2025 3:57 AM in response to Grant Bennet-Alder

I connected one 4k monitor via dp1.4 using a thunderbolt 4 cable, and the second using the HDMI port .

The dp1.4 using the thunderbolt 4 cable shows 60Hz, while the second using the HDMI port only shows 30hz. Why doesnt it show 60hz?

Also, I tried to connect 3 4k monitors, two using dp1.4 using thunderbolt 4 cable and one HDMI port/cable, and all show 60hz.

Also, when two 4k monitors are connecte via dp1.4 using thunderbolt 4 cable, they both show 60hz.

How come with 3 monitors connected in extended mode I can get 60hz across all of them, but when connecting just two monitors, where one is via hdmi, this hdmi one only gets 30hz?

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Answer 4

Jan 24, 2025 7:09 AM in response to PetrolMan

What I read form your report above is that the display you connect with HDMI can not get higher than 30 Hz.

You display appears to be limited (by the DISPLAY) to HDMI 2.0, which has a slightly lower data rate, and tops out at 4K at 50 Hz (but that may not be a section that is offered.)

if you turn off HDR, or reduce the resolution to 2K, the display should run at 60 Hz without issues over HDMI.

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Answer 5

PetrolMan Author

Level 1

8 points

Jan 23, 2025 11:22 AM in response to Grant Bennet-Alder

thanks for the feedback.

do you know what 4K 10bit hdr monitors would support Thunderbolt Display?

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M2 Max daisy chain dual extended displays using only one thunderbolt port

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