I’ve recently switched docks for my laptop to a dell-made dock, and have noticed that it won’t recognize my Anker USB Hub – a windows error dialog claims “too many USB hubs”, and it further suggests that I’ve exceeded a 5 hub-connection-limit.
Repro:
Dell Latitude 9420 laptop running Windows 10 20H2
Dell WD22TB4 thunderbolt 4 dock
l1techs kvm – my flavor is a 5 gigabit “Display Port 1.4 KVM Switch - Dual Monitor”, purchased in April 2021. Connected to dock with usb a-to-b cable
Anker 7-port usb 3.0 hub – plugged into USB port of kvm, not the HID
No matter what ports I try in any configuration of the above, the hub won’t be recognized if I plug into the KVM. If I plug the same hub straight into the LT or Dell dock, it works straightaway. No other peripherals are connected. The kvm works like a dream in every other configuration, just not with this dock.
I’ve had this exact setup working previously with a Lenovo dock instead, so I’m speculating that there’s some kind of compatibility or driver issue with this dell thunderbolt 4 dock. Dell’s done me dirty plenty in the past, and other posts here have anecdotally reported issues with Dell docks as well.
Distrust of Dell aside, I’m curious if anyone has experienced anything similar, and if there are any workarounds possible that still utilize the KVM. Also, possible long shot, but is this an issue that might be mitigated with improvements baked into the recent versions the l1techs KVM? Thanks for any insights.
Update: I tested a non-powered 4-port anker hub into the KVM instead, which sort of works – a wireless mouse receiver and webcam worked, but not a razer USB Mic – that one triggered the usb hub error. As did a keyboard that has USB passthrough on it. So I’m even more inclined to blame Dell jiggery-pokery and some sort of problem with how they’re handling USB devices.
This sounds like an actual USB limitation. If I chain all the USB hubs I own i can also get to a nesting level where devices get no longer recognized.
I do not know whether this is also a USB limitation or just a design choice, but all my Hubs that include more than 4 USB3 ports consist of 2 nested hubs as shown in USBTreeView.
So the WD22TB4 will most likely show up as up to 3 nested USB-Hubs.
(1) the Goshen Ridge TB4 controller when connected in USB4 mode
(2) one will be the 10G USB3 hub inside the dock
(3) depending on which USB-Output you use you get one directly from hub 2 or yet another level deeper.
(4) the USB hub inside the KVM
(5) Anker hub, which on USB3 should also show up as 2 nested Hubs
So it seems very possible that this might actually exhaust USBs capabilities.
I could reach that limit as well by chaining my WD19TB in USB-compat mode (1 hub), a Caldigit Element Hub (in USB-compat mode, 2 hubs), a Dell Monitor (2 hubs) and another monitor-integrated hub (1 hub) and if I then attach another USB-C hub I reach the limit and the last hub no longer gets recognized.
But this also means, that you can flatten this hierarchy by choosing different USB ports at various stages. The TB-outs of the WD22TB for example should come directly off of the Goshen Ridges integrated hub (so (1)), the 10G ports on the WD22 should be one level deeper (2), while the 5G ports seem to be the deepest (3)…
Rear or front port for 3.0? It probably won’t matter too much. The anker hub itself may have two hubs built in to get so many ports. i.e. 1 4 port hub plugged into another 4 port hub “electrically”
usb tree viewer may be useful there.
If you can bypass the dock and plug the kvm straight into the laptop with the dock that’ll also eliminate the issue and be more reliable.
I use the WD19 dock with the kvm and it works fine but I don’t have an extra hub.
thunderbolt is only only 40 gigabit anyway. You’d have more bandwidth with thunderbolt dock + separate usb kvm connection than through thunderbolt. If you have a high res/refresh dp1.4 display you’re using 32 gigabit of that 40 gigabit with the dp1.4 signal anyway. At least in one direction
We should have been on 80 gigabit thunderbolt ages ago. It is so so dumb for power users that we’re still plugging along with 40 gigabit for… almost a decade… now
usb tree view may give you some clues as to which ports in the dock are “native” and which ones are hanging off of an internal hub there, too, there may be one or two ports not hub-ized by the dock.
It didn’t appear to make any difference whether I used front or rear. There was indeed a layer of nesting on the Anker hub, which shows up on the Tree Viewer image below.
I never thought to do this and it worked with some tweaking – thanks very much for the insight. The tweaking needed was to distribute some of the devices so not everything went through the L1T KVM, in particular a Logitech BRIO webcam which presumably eats up a lot of bitrate.
This is absolutely what happened – It’s wild to me that the hub itself contains three levels of nesting before you hit USB headers. I’m an absolute USB teetotaler, but surely that isn’t necessary? As an added thought, my previous lenovo dock had just usb 2.0 headers and no thunderbolt, so no doubt less nesting was involved. The image of the Wendell-suggested tree view is below.
Yeah this problem actually became worse with TB4/USB4 because every Hub / Controller must now contain a USB3 hub, whereas with TB3 it was its own Root Controller (or in compat mode, just bypass).
And due to the modularity of those Dell docks (the left part only contains the TB-controller, the USB-hubs are separate in the right part) and it still offering you 2 TB-outs, there has to be at least one additional USB3 hub in there in order to get more than 1 USB port out of it. The second one seems to be only because it requires more than 4 USB3 ports (3 at back, 2 at front + ethernet).
Same with my CalDigit Element Hub. Only the TB-Outs use the USB hub integrated into the TB controller. The USB-A ports are from a separate USB hub, because I believe Intels TB-controllers only have their TB-outputs plus 1 additional USB3 port (and the PCIe port, but that is unused with the Dell docks).
So actually USB3 performance through an entire topology of USB4 devices is worse, because now they all have to share 10G in total, where with TB3 each one would be its own USB controller with slightly above 10G worth of bandwidth across its root ports, only sharing the larger PCIe bandwidth…
