Malcolm Owen
Some M4 Mac mini owners are discovering USB-C issues with their new desktops, with peripherals disconnecting seemingly at random.
USB is a fairly resilient technology, with the expectation that things connected using it will typically remain functional for a very long time, outside of external effects. However, it seems that in a small number of cases, USB-C connections on the M4 Mac mini are problematic.
Various Internet posts uncovered by AppleInsider reveal that users are undergoing similar problems. They generally consist of hardware connected using USB-C suddenly disconnecting and becoming unusable, or not connecting in the first place.
Going down
The reports uncovered in its investigation cover a range of time, ever since the M4 Mac mini's release in late 2024.
In one Reddit example posted on January 15, a poster explains that their USB-C keyboard "intermittently disconnects" and requires a physical disconnect and reconnect to start working again. To rule out other hardware issues, the same keyboard was working fine on the user's other Macs, with the issue only manifesting on the M4 Mac mini.
Other respondents complained that they had similar issues when using docks connecting with USB 3, as well as a KVM switch failing to work after waking the Mac mini. After a physical disconnection and plugging it back in, everything worked fine.
Another said it was only an issue with the rear ports, as the freezes didn't manifest when using the front ports.
A post from the end of December also asked if users had power issues with USB-C devices working off the M4 Mac mini. An external hard drive attached via USB-C disconnected when an "I/O heavy" task was performed, even when directly connected.
Others raised their problems again, with hubs not working with the ports but still working elsewhere. Questions were raised over the power draw of connected devices, as well as whether it was a front or rear USB problem, though it seems not to be limited to the rear set.
There are front ports on the new M4 Mac miniAn earlier post from November also brought up a failure in hub connectivity. However, in that instance, the poster said they were using an external power source for the hub instead of relying on bus power.
One respondent in that instance said that their USB-C devices didn't reconnect automatically on their M4 Mac mini, unlike their M1 Mac mini. Again, they had to physically reconnect the devices for them to work.
The issue has also appeared on the Apple Support Forum. One November 23 post explained that the front USB-C ports worked fine, but the rear ports wouldn't work reliably with connected devices, effectively making the rear ports useless.
Replies also included others who had similar problems, with hard drives connecting to USB-C at the front working, but not mounting to the rear.
These signal dropouts can be annoying to users and can be down to a number of reasons.
Elsewhere, the same problem appeared on the MacResource forum, with a user reporting a similar issue. They discovered that the Apple Extended Keyboard didn't work around the back when plugged in via an adapter, but a Logitech mouse plugged in directly worked.
The front ports apparently worked fine in that case.
Puzzling problem
The issue is a difficult one to diagnose, due to the sheer number of variables at play. Since users have complained that it happens when their hardware sleeps, this may also be something that Apple could issue a software update to fix.
Away from Apple, most users may find that they can do a number of checks to make sure it's not a problem they inadvertently caused. Inspecting the cable for damage, including looking for debris in the ports, will help, as well as trying a known-good cable in the setup.
The use of cheap USB-A to USB-C adapters and hubs may also be causing issues, as can poorly constructed cables. Checking these and replacing them if warranted could help the situation for the average user.
There should also be some thought about what devices are connected to which port on a Mac in general. It's not a good idea to have multiple bus-powered devices drawing power from the same single USB-C port on a host Mac.
Something like this could be solved with a powered hub or dock.
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Christine McKee
Andrew Orr
William Gallagher
Andrew O'Hara
Charles Martin
5 Comments
I have some USB-C speakers I plug into the back of my Mac mini that are doing that. I noticed it happened mostly when I would use my AirPods in the mornings before everyone got up, and tried to switch back. Sound would be coming from the Mini and not the speakers. The only way to fix would be to unplug and replug them in. I then ran a second USB-C to the speakers PD port to essentially 'power' them, but I still find that it will fall back to the internal speakers at odd times (after sleep, first use in the morning, after using AirPods), but then in the last week, I haven't had any issues.
Got my M4 Pro Mac mini (64GB Ram,10Gb ethernet and 2TB SSD) two days ago.
Overnight, Migration Assistant successfully moved everything via WiFi from my M2 Pro Mac mini (32GB Ram, 10GB Ethernet and 2TB SSD) to the new unit.
Both units had their own Magic Keyboard and my Logitech mouse has 3 switchable Bluetooth connections so it worked with both devices. Had to constantly switch the Apple monitor cable for the Studio Display between the two units to get Migration Assistant going. I had the keyboard connected with a Lightning to USB-C cable to one of the M4 Pro front USB-C slots.
Once done, I added the USB-C cable to the Raid drive to the new mini on the back along with the Studio Display cable. The Logitech mouse and new Magic Keyboard connect vis Bluetooth. I had issues with the Studio Display because I used the prior LG monitor's cable. Putting the Apple Display cable that came with it cured the waking up of the screen issue.
So far so good. Also SMP and VNC connections over 10Gb ethernet worked where they did not on the prior unit. Both units were on MacOS 15.2 operating system.
Wondering if the issue with the earlier M4 mini models could be operating system issues if not on latest release? Or, perhaps the issue did not happen with the M4 Pro chip models?
Is USB really a resilient interface? I recently worked a contract where test stations in production would often start reporting errors in the middle of the tests because some of the equipment was connected using USB and it would intermittently disconnect. This is compared to HPIB/GPIB which is old, bulky and slow but extremely robust.
Well known (on internet) that Apple wired USB keyboards dont work on the M4 mac mini whereas 3rd party keyboards work. Easily reproducible.
I had an issue with my HooToo USB-C hub failing to connect to my new M4 Pro mini after I had done a cable migration off my 10yo 27"iMac when connected to the rear port only. On the front port it was fine. Several re-boots seemed to fix the issue. It stopped flashing. HooToo hub was bought for my 12" MacBook years ago, which had CPU issues and was scrapped.