USB Hubs & Mac System Report - confusion

I have an Anker 9 port USB 3.0 hub attached to my iMac. I was trying to find out if my hard disk was connected at the top speed of the hub. When I do a System report and after a lot of unplugging and plugging in to find out which is which in the report, I see that the report splits the Anker USB 3.0 connections as one “hub” and the Anker USB 2.0 connections as another “hub”. To make things more confusing, the report sticks in a few other connections which aren’t part of the Anker hub. Why not simply list the Anker Hub as as the top level and then list all the connections under it OR at least then have the sub hubs 3.0 and 2.0?

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I am guessing, but because the USB 3 chipset runs the USB 3 side of the hub and a separate USB 2 chipset runs the USB 2 side of the hub. To the OS, those are two separate devices, it is only your eyes, seeing one housing for the two devices that turns it into one device… :wink:


This is precisely how USB 3.x hubs and hosts work. All USB 3.x hubs are actually two hubs in one. One hub handles USB 1.1/2.0 traffic using two wires to the host (called D+ and D-). The other hub handles USB 3.x traffic using 2 sets of 2 wires called SSTX and SSRX.

It was important to do it this way to maintain backward compatibility (ie, a USB 2.0 device attached to a USB 3.0 hub only touches one of the two hubs, and completely ignores the USB 3.x one).

Things get even MORE complicated when you make the jump to USB4… where every hub is actually 4 distinct devices:

  1. USB 1.1/2.0 hub
  2. USB 3.x hub
  3. USB4/Thunderbolt router
  4. PCIe Switch