Samsung ViewFinity S9 5K monitors disconnect on Mac Studio

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Samsung ViewFinity S9 5K monitors disconnect on Mac Studio

I'm experiencing a very strange issue with two Samsung ViewFinity S9 (S27C900P) monitors connected to a Mac Studio M3 Max.

My setup:

- Mac Studio M3 Max

- macOS Sequoia (latest version)

- 2x Samsung ViewFinity S9 (S27C900P) 5K monitors

- Both monitors connected directly to the Mac Studio

- Tested with original Samsung Thunderbolt cables

- Tested with Apple Thunderbolt 4 cables

- UAD Apollo Twin X + UAD Satellite connected via Thunderbolt (daisy chained separately from the monitors)

Symptoms:

Randomly, one of the monitors disconnects. It is not always the same monitor. Sometimes the left display disappears, sometimes the right one.

When the issue occurs:

- macOS only shows one display in System Settings > Displays

- The disconnected monitor displays a message saying there is no DisplayPort connection and that it will power off after 60 seconds

- Disconnecting and reconnecting the Thunderbolt cable does not fix the issue

- Turning the monitor off and back on does not fix the issue

- The only reliable way to recover the display is:

1. Unplug the monitor from AC power and reconnect it, or

2. Restart the Mac Studio

Additional information:

- Sleep is disabled

- Display sleep is disabled

- The issue happens intermittently and I have not found a specific trigger

- Since either monitor can fail, I do not believe this is a defective panel

- Both monitors operate normally once they reconnect

I would like to know:

1. Has anyone experienced similar issues with dual 5K displays on Apple Silicon Macs?

2. Has anyone experienced this specifically with Samsung ViewFinity S9 monitors?

3. Is there any known Thunderbolt, DisplayPort, or macOS issue that could cause a display to completely disappear from macOS until the monitor is power-cycled?

Any suggestions would be greatly appreciated.

Mac Studio, macOS 26.5

Posted on May 26, 2026 9:38 AM

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Answer 1

May 26, 2026 7:26 PM in response to jotaceworld

more recent versions of macOS have become increasingly insistent that NO transmission errors are detected in operation. if any are detected, the display will drop out. The most common reason for errors is cables that are inadequate or too long.

Substituting different cables is a check against cables that are BROKEN. It does nothing for cable that are low spec or too long.

Could you please affirm that the ThunderBolt cables you are using have the thunderbolt symbol on each end are are no longer than 0.5 meters in length, or if longer, are PRO or ACTIVE cables?

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Answer 2

May 26, 2026 2:11 PM in response to jotaceworld

that Samsung appears to be a 5120 by 2880 (5K) display at 10 bits/color and refresh rates from 30 to 75 Hz.

interfaces include:

Thunderbolt-4, providing uo to 90W power delivery

[mini] DisplayPort

USB-C explicitly limited to DATA-ONLY.

Samsung does not appear to provide specs for their included thunderbolt cable.

Ordinary certified ThunderBolt cables (with the Thunderbolt symbol on each end) are limited to 0.5 meters for this high-end application.

Longer ACTIVE or PRO cables, containing signal re-drivers, are available, but can be expensive.

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Answer 3

jotaceworld Author

Level 1

5 points

May 26, 2026 4:07 PM in response to Grant Bennet-Alder

Thank you for the information.

I have already tested multiple Thunderbolt 4 cables, including the original Apple Thunderbolt 4 cable and the Samsung-supplied cable. I have also tested different Thunderbolt ports on the Mac Studio.

The issue still occurs randomly on either of my two Samsung ViewFinity S9 monitors.

When the problem happens, the affected monitor completely disappears from both macOS Display Settings and the Thunderbolt device tree. Reconnecting the cable does not restore it. The monitor only comes back after either power-cycling the monitor or rebooting the Mac.

Because the issue occurs with different cables and different ports, I am trying to determine whether this is a known Thunderbolt/macOS compatibility issue or a ViewFinity S9 firmware issue.

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