X570 USB Root Hub Bandwidth Question

[glenimp617]

Hello Everyone,

Not an issue, more of a technical question as I'd like to understand more about how it works.

Yesterday I purchased 3 * USB2 webcams and originally wanted to connect them all through an external USB3 powered hub. Unfortunately only two of the webcams worked.
When I moved the third directly into the back of the PC, next to where the hub was connected it also failed to work.

My motherboard is an MSI X570 Tomahawk with the following on the rear panel

USB 1/USB 2 (root hub1 USB2) << Never used these ones
USB 3/USB 4 (root hub2 USB3 5Gbps) << This is where I had the camera and hub connected

I'm unsure if these share a single hub or not
USB-C 5/USB 6 (root hub 3 USB3 10Gbps)
USB 7/USB 8 (root hub 4 USB3 10Gbps)

When I moved the third webcam to another port lower down, it all started to work great.

It seems like the root hub didn't have enough bandwidth available for all 3 webcams (even though they are only USB2). Even if the webcams maxed out the USB2 bandwidth, there should have been loads left?

any ideas?

 

[glenimp617]

I think I've figured it out. Even if you connect USB2 devices into a USB3 port, inside the root hub still has the limitations of USB2 for USB2 devices.
Assume I could have connected a USB3 camera and that would have worked fine.

 

[Mcnumpty2323]

I think I've figured it out. Even if you connect USB2 devices into a USB3 port, inside the root hub still has the limitations of USB2 for USB2 devices.
Assume I could have connected a USB3 camera and that would have worked fine.

That sounds reasonable
It can probably automatically detect the devices usb version/capability
Bit like shoving a usb 2 flash drive into
A usb 3 port
Still going to get usb 2 speeds