Hello,
Thank you for contacting Plugable support! Sorry to hear about this issue. I’d be more than happy to assist you.
To be fully up front, and unfortunately, at this time there is no solution for this behavior and a firmware update will not help in this case. The root of the performance difference occurs when using this dock with Apple M series processor based systems. These systems use an Apple provided Ethernet driver (built into macOS) that controls the Realtek RTL8153B Ethernet chipset in the TBT3-UDZ docking station. This problem should affect any product using this Ethernet chipset as well to my knowledge, so it is unfortunately a widespread issue across the industry.
The Apple provided Ethernet driver being used is not optimized for newer M series systems, the driver is an emulated driver vs a native driver. So for example, older Intel Macs (and x86/x64 Windows or Linux based PCs) do not experience these kinds of issues because the driver was written for that platform, but for the newer M series processors the driver is being emulated to work on the new M series platform (Arm) and this can cause performance losses to occur. At this time Realtek does not offer a stand-alone driver to install that is optimized, currently only the Apple provided driver is available.
You should be able to verify this by going into the Mac System Report → Hardware → Ethernet and look at the driver field for the Ethernet chipset (“USB 10/100/1000 LAN”). You should see for the Realtek Ethernet in the TBT3-UDZ it’s using the emulated driver:
com.apple.DriverKit.AppleUserECM
Typically in cases where users encounter speed issues the best workaround would be to bypass the TBT3-UDZ Ethernet with a external USB Ethernet adapter (connected to one of the dock USB ports) that does have a native macOS M series driver available. As an example, the newer Realtek RTL8156B 2.5Gbps Ethernet chipset runs from the native driver (com.apple.driver.usb.cdc.ncm) and offers full performance - an example of this would be: https://plugable.com/products/usbc-e2500
It is also possible that Realtek or Apple may be able to release an updated native driver for the RTL8153B chipset, but I do not have any estimate for if or when that may occur. My apologies.
Please don’t hesitate to let us know of other questions.
Thanks again for contacting Plugable support and best wishes!
Joshua Henry
Senior Engineer | Product Owner
Plugable Technologies
