User profile for user: CMala
CMala Author
User level: Level 1
17 points

Dual Monitor Studio Display XDR fails on MacBook Pro M3/M4 Pro

Studio Display XDR in Dual Monitor configuration fails. It only work on one monitor. Tested with two different Macbook Pro with M3 and M4 Pro chips from two different users.


I can't connect two Studio Display XDR with Nano coating simultaneously to my Macbook Pro M3 Pro or to my wife's Macbook Pro M4 Pro. Both laptop have the "Pro" chip.


  • Both gorgeous display work individually.
  • I contacted Chat Support and they want me to bring the Mac to an Apple Store, saying it's the Mac that could be the problem. But then I tested with my wife's more recent laptop, and I have the same issue.
  • Both Macbook Pro have the latest MacOS Tahoe 26.3.1 (25D2128)
  • Both Macbook Pro have different users. The only software in common that could remotely maybe affect this is maybe Backblaze, CleanMyMac, and Microsoft Defender.
  • When I connect both, only one works. The second one gets online when I unplug the working one.
  • I tried all port/bus configurations (one on the left, one on the right, all on the left, etc.)
  • I tried daisy chaining the displays.
  • I tried lowering the refresh rate to 48 hertz on both display to limit thunderbolt bandwidth.
  • I tried with the laptop lid open or closed.
  • I tried powering the Macbook Pro with the magsafe cable.
  • I tried putting one of the display on another electric socket in the room.
  • I tried rebooting the Macbook Pro and unplugging both displays for 30 seconds.
  • I tried with displays already plugged or unplugged on cold laptop boot.
  • I tried all of this in all combinations on both laptops.
  • I tried Option key in the Settings/Display panel and clicked on Detect Displays. Never worked. The lack of feedback is unsettling.
  • I used the original Thunderbolt cables bundled with the displays.
  • It might have worked once.. I'm unsure if I dreamed.
  • I did this research with Gemini: https://gemini.google.com/share/a8ee184397e8


Consulted pages:


Feedback 1: the lack of visual feedback on the screen when you plug stuff is unsettling. Same for the Display Settings button. Please fix this!


Feedback 2: the Settings\Displays panel is easy to get to crash. I can get weird error codes and weird broken UI if I play enough with all the settings and plugging / unplugging the cables for long enough. For example "Extension process `Displays(5204)` exited.". Please polish this code!


Macbook Pro Specs

  Model Name:	MacBook Pro
  Model Identifier:	Mac15,7
  Model Number:	Z1AG001C6LL/A
  Chip:	Apple M3 Pro
  Total Number of Cores:	12 (6 Performance and 6 Efficiency)
  Memory:	36 GB
  System Firmware Version:	13822.81.10
  OS Loader Version:	13822.81.10
  Serial Number (system):	CC20LXYKN9
  Hardware UUID:	E28ADB17-44E6-5AC9-A0FD-2E6310A1DC03
  Provisioning UDID:	00006030-000251E23A82001C
  Activation Lock Status:	Enabled


Display 1 Specs

Studio Display XDR:
  Vendor Name:	Apple
  Device Name:	Studio Display XDR
  Mode:	USB4
  Device ID:	0x7901
  Vendor ID:	0x05AC
  Device Revision:	0x3
  UID:	0x80877E1D82CC4C00
  Route String:	1
  Firmware Version:	66.14
  Port (Upstream):
  Status:	Device connected
  Link Status:	0x2
  Speed:	40 Gb/s
  Micro Firmware Version:	1.13.0
  Port:
  Status:	No device connected
  Link Status:	0x7
  Speed:	Up to 40 Gb/s
  Micro Firmware Version:	1.13.0


Display 2 Specs

Studio Display XDR:
 Vendor Name:	Apple
 Device Name:	Studio Display XDR
 Mode:	USB4
 Device ID:	0x7901
 Vendor ID:	0x05AC
 Device Revision:	0x3
 UID:	0x80877E1D8089AB00
 Route String:	1
 Firmware Version:	66.14
 Port (Upstream):
 Status:	Device connected
 Link Status:	0x2
 Speed:	40 Gb/s
 Micro Firmware Version:	1.13.0
 Port:
 Status:	No device connected
 Link Status:	0x7
 Speed:	Up to 40 Gb/s
 Micro Firmware Version:	1.13.0


Any help appreciated, specially from the Studio Display XDR team at Apple. If you guys want to sell more displays... :-)

Studio Display XDR

Posted on Mar 14, 2026 12:53 PM

Reply
Question marked as Top-ranking reply
User profile for user: robgmsft
robgmsft
User level: Level 1
8 points

Posted on Apr 19, 2026 5:54 PM

TL;DR — for anyone skimming:


If you have two Studio Display XDRs and only one lights up at a time on your M4 MacBook, the evidence so far points to a bug in macOS Tahoe 26.4.1 and/or the display firmware that shipped with it, not your hardware or setup. The one-at-a-time behavior appears to have started right after the display firmware update that runs during the Tahoe install. (Caveat: this read comes from an AI-assisted log dive — it's the most likely cause based on what the kernel log shows, but it hasn't been confirmed by Apple.)


Probably won't help (and here's why):

- Taking displays to the Apple Store / swapping them — both units work individually, and others are hitting the same behavior with different serial numbers, so a swap would likely just give you a new pair with the same symptom.

- Reinstalling macOS — if the bug is in macOS itself (likely), reinstalling installs the same bug. A fresh user account was tested first (same behavior), which is basically a preview of a reinstall.

- Buying a new Mac / upgrading to M5 — if this is an OS-level issue, a newer chip running the same Tahoe would probably hit the same wall.

- Cables / ports / docks / dongles / resolution / refresh rate / color settings — none of the usual knobs seem to move this; the failure appears to happen before the OS reaches those settings.


What's worth trying:

1. File a Feedback Assistant report at https://feedbackassistant.apple.com — volume drives priority. Mention it's the dual-Studio-Display-XDR one-at-a-time issue on Tahoe 26.4.1. If you want a specific string to cite, AppleT603XDisplayCrossbar + allocated: 0 are the log phrases that came out of my diagnostic; Apple's Displays team can tell you if that's the right pointer.

2. Use one display for now. Both work individually. Swap the active one when you need to.

3. Watch for macOS 26.5 / a firmware update. This has the shape of a point-release fix rather than something a hardware revision would address — so a new Mac or new display is unlikely to get you around it.


TLDR on the TLDR: this looks like an Apple-side bug based on the evidence, so returning gear or reinstalling probably won't help. Best bet is filing feedback and waiting for a software fix. Not 100% confirmed — but the workaround path (buy new stuff / reinstall) is a lot of effort for a low expected payoff.

View in context
83 replies
User profile for user: Grant Bennet-Alder
Grant Bennet-Alder
User level: Level 10
145,275 points

Aug 11, 2026 11:45 AM in response to berkeleyboo

<< "Doesn't work " >>


.. is far too vague a symptom to help you debug, and there are lots of users for whom these displays work just fine.


EXACTLY what are your symptoms.complaints?


...and exactly what model Mac are you connecting to, including processor type Mnnn {(plain), PRO MAX, ULTRA}


... also, you would be FAR better off and getter better results by starting a new discussion, rather than just tacking your issues on the end of this (far too long) discussion thread.



Reply

Dual Monitor Studio Display XDR fails on MacBook Pro M3/M4 Pro

Welcome to Apple Support Community
A forum where Apple customers help each other with their products. Get started with your Apple Account.
Learn more Sign up