Mac Mini M4 Intermittent Thunderbolt/USB4 Disconnection Issue with Fideco(ASM2464PD Chipset) USB4 M.2 SSD Enclosure

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Mac Mini M4 Intermittent Thunderbolt/USB4 Disconnection Issue with Fideco(ASM2464PD Chipset) USB4 M.2 SSD Enclosure

Mac Mini M4 (24GB RAM / 512GB SSD): Intermittent Thunderbolt/USB4 Disconnection Issue with Fideco M40 SSD Enclosure (ASM2464PD Chipset)

I have a 2TB Samsung 990 EVO Plus SSD installed in a Fideco USB4 enclosure (using the ASMedia ASM2464PD chipset). I have been experiencing frequent random disconnections of the external SSD with my Mac Mini M4 (latest macOS Tahoe 26.2). After several days of testing, analyzing system logs, and updating the Fideco M40's firmware to the latest version (from 54.17 to 57.17—aligning with the most recent ASMedia ASM2464 NVMe/USB4 controller firmware available on sites like station-drivers.com, version 230525_85_00_00), the issue persisted.

The Mac Mini M4 system logs indicate that the system and enclosure are struggling during DarkWake states and recurring Maintenance Sleep cycles.

/var/log/asl:
...
AMPDeviceDiscoveryAgent[696]: Entered:_AMMuxedDeviceDisconnected, mux-device:23
...

/usr/bin/pmset -g log:
...
[AppleT8132PCIeC driver is slow(msg: SetState to 0)(1675 ms)]
[IOThunderboltControllerType5 driver is slow(msg: SetState to 0)(1723 ms)]
...

This appears to be related to a PCIe tunneling power state timeout, possibly due to strict timing constraints in the Mac Mini M4's PCIe HAL (limited to <1500 ms or so). Until a newer firmware is released by ASMedia, the enclosure manufacturer (Fideco) or Apple, the most reliable workaround I have found and tested is to prevent the Mac Mini M4 from entering deep sleep modes (S3/S4).

I hope this helps others facing similar issues. Any better solutions are highly welcome.

Command to disable system sleep (via Terminal):

Bash

sudo pmset -a sleep 0 disksleep 0 displaysleep 30

This keeps the system awake (preventing deep sleep), allows disks to stay active, and lets the display sleep after 30 minutes for power saving. You can adjust displaysleep as needed. Note: This increases idle power consumption slightly but resolves the disconnection problem in my setup. To revert, use

sudo pmset -a sleep 1

Additional Notes:

Many users report similar Thunderbolt/USB4 external SSD disconnection issues on the M4 Mac Mini, often tied to sleep/wake cycles, power delivery, or chipset compatibility (especially with ASM2464-based enclosures). Common suggestions include using a powered Thunderbolt hub, ensuring good cooling for the enclosure, or testing different cables/ports. If the problem continues, consider checking for macOS updates or contacting Apple Support.

Mac mini, macOS 26.2

Posted on Dec 25, 2025 2:46 AM

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Answer 1

Dec 25, 2025 5:13 AM in response to i728

FWIW, I have an OWC Express 1M2 US4 enclosure that uses the identical chipset and have zero issue using it as a boot drive. I bought it packaged with an OWC SSD Aura Ultra IV.

It is not uncommon for some combinations of SSD and enclosures to be problematic. I have seen test reports of some enclosure combos that work great on Macs but are unreliable on PC's and visa versa. Also, within manufacturers, like Samsung I have seen PRO series SSDs have amazing and reliable performance on a given enclosure but EVO series SSDs being problematic in the same enclosure.

So, regardless of what manufacturers may say, not all enclosures and drives are plug and play especially with the high performance once such as Thunderbolt 3/4/5 or USB4. Generally, if manufacturers do not specifically state or have tested enclosure/drive combos, the right combo can be a coin toss.

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Answer 2

den.thed

Level 10

91,186 points

Dec 25, 2025 7:56 AM in response to i728

The default automatic computer sleep has been an issue for some time now with different setups.

This issue is not limited to macOS Tahoe 26, your M4 Mac mini or your external USB device.

I'm no expert, but the pmset's for Intel Mac's may not work the same on Silicon Mac's.

As a test

Go to System > Settings > Energy > Turn On "Prevent automatic sleeping when display is off"

Go to System > Settings > Lock Screen > set "Turn display off when inactive" to 10 or 30 minutes

Leave the Mac Mini On and only allow the display(s) to turn Off on the timer

Do not manually Sleep from the Apple Drop Down menu over night

Shut Down the Mac mini when away for a day or more

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