TBT3-UD1-85W Thunderbolt running at slower speed

Hello all. I just received my TBT3-UD1-85W docking station yesterday. I really love this device, as it seems to have RESOLVED my issue with my LG 27UL600-W 4K UHD IPS LED Monitor. It’s connected via the DisplayPort+++ port on the Plugable. The monitor loves this connection. Finally, able to use LG’s original DisplayPort connection. Picture looks the best ever! Amazing… I’ve extremely happy about that.

The negatives… I’ve got it connected to my 2020 Mac M1 Mini 8g RAM 256g SSD. I am running my OS off of a Sabrent Rocket XTRM 2TB NVMe SSD. Connected directly to the Mac I get 2.2TB/sec write and 3.0TB/sec read. Plugged directly into the docking station I get 1.5 TB/sec write and 2.5TB/sec read. Thunderbolt is clearly running at slower speed. My Samsung EVO 1TB drive experiences similar cut in speed. Both USB3 ports are not recognized and elicits an error "USB accessory needs power connect Apple USB to USB port on this Mac”. The compromise (sort of) is to plug my Sabrent NVMe SSD directly into the MAC (by the way great solution to paying so much to Apple for storage).

I love that my monitor looks better than ever in its native 4K picture now. I no longer seem to have the resolution issues coming out of sleep or reboot. Just for those reasons, I will keep this device. But it would be nice to be able to have that other Thunderbolt3 connection free for more flexibility.

And I occasionally plug in the Mac USB Superdrive to copy DVD’s, so a fix for the USB ports would be great. There must be a solution since I’m not seeing anything on the boards. I will continue to of course evaluate the product and report back any discoveries.


Thank you for posting, and we are glad that overall you are enjoying your new TBT3-UD1-85W docking station!

  • The total available bandwidth between the host system (your Mac mini) and the docking station is 40Gbps. The different elements within the dock such as the video output, USB host controller (which in turn drives the dock’s USB ports), audio ports, etc. all require a certain amount of bandwidth in order to function. As a result, you may see reduced performance of Thunderbolt 3 devices that are connected to the dock’s ‘downstream’ (aka second) Thunderbolt 3 port as compared to when they are directly connected to the host (this is expected behavior).

  • You mention that, "Both USB3 ports are not recognized and elicits an error “USB accessory needs power connect Apple USB to USB port on this Mac”.” and later on you mention that you are using an Apple SuperDrive. My impression is that you receive that warning message only when you are connecting the SuperDrive to the docking station’s USB ports. Please correct me if I am mistaken.

Assuming for the moment that my understanding is correct, the Apple SuperDrive requires more power than a standard USB 3.0 port can provide and unfortunately is not compatible with the TBT3-UD1-85W. As a result, I would suggest connect the SuperDrive to one of the USB ports built-in to your Mac.

Thank you,

Plugable Technologies

Hello Bob,

Thank you so much for the super fast reply. First point, I didn’t think about sharing the 40Gbps pie with DisplayPort (which again I’m loving) and the Samsung SSD downstream. Makes total sense to me. I can live with the lowered bandwidth on the Samsung SSD as it’s just a SSD data drive.

Second point, great point and yes you are correct, I plugged the SuperDrive into both ports on the Plugable doc. I now see it was a message that the drive must be directly connected. Not an error. I have validated all USB ports work as designed. Bob this resolves all my issues thank you very much. Again, great product! I highly recommend.

Kind Regards,

Hi Bob,

Additionally just to further the point you made. I moved the LAN connection back to the Mac and now my Samsung SSD is connecting 70GBs faster, which is about what it was getting directly connected to the Mac. I’m thinking it reduces additional bandwidth resources from the Doc. I like it even more.


Hi Carleton,

Thank you for getting back to us with the updates, and you are of course most welcome for the help. I am glad the information we provided was helpful.

Please let us know if you need any help in the future, and please have a good day!


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