MacBook Pro M5: Can't use two external monitors

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Level 1

4 points

MacBook Pro M5: Can't use two external monitors

I have a new, MacBook Pro with the M5 chip that purportedly supports 2 external monitors. My monitors are two AlienWare AW2725Q QD-OLED 4k UHD 240hz 0.03ms monitors with HDMI and DisplayPort

When connecting the monitors, I have tried using two Apple usb-c adapters connected HDMI cables to the monitor. I have tried one HDMI cable connected to the HDMI port and one to using the Apple usb-c/HDMI adapter. I have tried every combination of ports and cables, to no avail.

In every combination of cables, I cannot get and pair of two connections to run two external monitors simultaneously. I have no issue with any single connection working. If I plug both in only one monitor displays. If I unplug that working monitor, the non-working monitor, regardless of which port, which type of connection it uses, will light up.

I have tried everything I have found online. I have power cycled all devices. I have tried the options key when on the display page but nothing shows up, I have tried the <cmd> F2 without result.

I have played around with the monitor resolution and am currently running at 1920 x 1080 at 60htz.

I have lightly used Macs in the past. But bought this new MacBook with a plan to use Mac as my main platform going forward. Almost all of our house is Apple enabled.

(Both of these monitors work fine with my 2022 Lenovo x1 Carbon. Easily.)

Any help would be appreciated!

MacBook Pro (M5, 2025)

Posted on May 9, 2026 11:39 AM

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Answer 1

Top-ranking reply

tihenry

Level 1

18 points

Aug 31, 2026 9:14 PM in response to BEHurst

This issue has been discussed here. This issue stems from how the system allocates display pipeline bandwidth. By default, it allocates the maximum bandwidth a monitor can handle. For the AW2725Q, that is 4K at 240Hz. Because running two of these monitors at 4K 240Hz exceeds the total display pipeline bandwidth of the M5 Pro, only the first detected monitor will display an image.

However, I found a workaround specifically for the AW2725Q:

Open the monitor's OSD menu.
Navigate to Game > Console Mode and set it to Legacy.

This forces the monitor to cap at 4K 120Hz (applies to HDMI only), freeing up bandwidth for the second display.

As long as the system detects the "Legacy mode" monitor first, you can successfully run both monitors simultaneously at 4K 120Hz!

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Answer 2

BEHurst Author

Level 1

4 points

May 12, 2026 11:48 AM in response to BEHurst

So i did confirm that both the HDMI cables are Ultra Hi-def.

I tried some different docking stations. I was able to get the Plugable Thunderbolt™4 16-in-1 Docking Station for MacBook Air/Pro (TBT4-UDZ) to work, with the two external monitors and a single Thunderbolt connection from the laptop.

I realize you have to have the right cables, even from my Windows laptop, but this is frustrating.

I will continue to try to figure out the why for my setup, but I can operate for now.

Thank you.

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Answer 3

May 12, 2026 6:59 PM in response to BEHurst

Part of the why is that the bandwidth required to drive ONE of those displays is essentially ALL of a Thunderbolt-3 or -4 Bus, or a DIRECT HDMI Bus out of the Mac.

comparisons to Windows are not helpful, because Windows allows you to configure any way you like, and the errors that occur are YOUR problem.

the Mac drops the connection if Transmit errors occur.

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Answer 4

May 9, 2026 12:15 PM in response to BEHurst

Displays at 4K over USB-C:

The following are limits based ONLY on the standards, NOT what the Mac is willing to supply:

USB-C Display data rates top out just under 20 G bits/sec., However, HDMI and DisplayPort both have speeds that increase only in discrete steps.

• HDMI highest step that fits inside a USB-C envelope is equivalent to HDMI 2.0, and runs at 14.4G bits/sec (spread over three data pathways plus a clock signal). Conversion of a USB-C signal to HDMI 2.1 is not reliable or practical.

A 4K display over HDMI (derived from USB-C) at 8 bits/color (HDR=OFF) can run NO faster than 68 Hz. A 4K HDR display at 10 bits/color (HDR+ON) can run NO faster than 55 Hz.

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• DisplayPort highest step that fits inside a USB-C envelope has a much higher data rate, HBR2, of 17.28 G bits/sec (spread over four data pathways).

A 4K display over DisplayPort (derived from USB-C or encapsulated in USB-C) can run NO faster than 81 Hz ay 8 bits/color (HDR=OFF). A 4K HDR display can run NO faster than 65 Hz.

--------

Conclusion:

DisplayPort over USB-C (or simply USB-C) connection can theoretically produce slightly faster and more reliable connections than HDMI derived from USB-C

Use of a ThunderBolt port can produce display data rates just under 40 G bits/sec. But Unless your display takes Thunderbolt directly, most practical adapters are not avaIlable as a dongle, and are built into Docking Stations.

The DIRECT HDMI port (in most Macs M2 and later) can produce HDMI 2.1 Display data even faster, at 42 G bits/sec. Special ULTRA cables required.

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Answer 5

May 9, 2026 12:12 PM in response to BEHurst

that Alienware AW2725Q display features

2x HDMI 2.1

DisplayPort 1.4

You will get great results using a DIRECT HDMI cable form the Macs HDMI port, provided you use an ULTRA rated cable. at 10 bits/color. refresh rates up to 144 Hz are possible without resorting to Display Stream Compression.

Using a 4K 10 bits/color display with an adapter/dongle from USB-C rapidly runs out of bandwidth, and is unlikely to work properly.

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Answer 6

May 11, 2026 1:37 PM in response to BEHurst

<< Monitor 1: T4 port->Apple AV adapter->HDMI cable->TV >>

That device is called the "Apple USB-C Digital AV Multiport Adapter". It is inherently a USB-C device, and as such is severely limited in its ability to drive a 4K display at anything higher than 30 Hz, especially a 10 bits/color device.

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Answer 7

BEHurst Author

Level 1

4 points

May 11, 2026 1:06 PM in response to BEHurst

Thank both of you for time, effort, replies and the insight.

As I’m sure you know, all three of the USB-ports on my Apple Mac are Thunderbolt 4 (T4). And based on what I’ve read, they should be able to handle the 2 monitors. The Mac also has an HDMI connection (and MagSafe).

So I tried 2 different methods of connecting.

Method 1: I used Apple’s AV connector (I bought a new one just in case) to connect a T4 port to an HDMI cable which I then connected to a monitor.

Monitor 1: T4 port->Apple AV adapter->HDMI cable->TV

I connected the HDMI port on the Mac to the the other monitor with a HDMI cable.

Monitor 2: HDMI port->HDMI cable->TV

The Result: Both monitors/connections worked, but not simultaneously. If both were plugged in, one or the other worked. (I detected no pattern in which one worked.) If only one connection was plugged in, regardless of which one, that one worked just fine. I did move the connected T4 port from port to see if it was a single port issue. It wasn’t.

Method 2: I plugged both monitors in using two Apple AV connectors. In this case, I used 2 T4 ports, one for each of the Apple AV connectors. Those were connected to two seperate, but identical HDMI cables.

Monitor 1: T4 port->Apple AV adapter->HDMI cable->TV

Monitor 2: T4 port->Apple AV adapter->HDMI cable->TV

The results were identical to the first method. Either one of the monitors worked, but I was unable to display on both of the monitors simultaneously.

—

I am going to check on the cable specs for the HDMI. But I bought these to drive a 46” curved screen ultra hi-def Samsung previously. So I think they should work. But I will confirm.

The only other cables/adapters I used were the Apple AV adapters, which per Apple should work.

So the puzzling part for me is either connection works fine. But not simultaneously. And there are no error messages I can see.

Any other thoughts?

Appreciate it.

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