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When I connect two USB2.0 devices to a USB3.0 HUB and that HUB to a USB3.0 capable Host computer, will link to the host computer be USB3 and thus support ~300 MBit? This would be my intuitive understanding. Or does the HUB, because it is USB2.0, somehow logically make the uplink also 2.0? Or does it depend on the hub?

I am having trouble using several USB 2.0 cameras at the same time, but I don't have USB 3.0 on the host side yet. So I'm wondering if a USB 3.0 HUB could help avoiding the bottleneck, if I have USB 3.0 on the host.

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  • \$\begingroup\$ No, you run at the lowest common denominator. \$\endgroup\$
    – Ron Beyer
    Apr 13, 2020 at 21:24
  • \$\begingroup\$ 300 Mbit? Where did you get that number? \$\endgroup\$
    – Oskar Skog
    Apr 13, 2020 at 21:33
  • \$\begingroup\$ @OskarSkog oh thanks, 300MBit is totally off, I hit the wrong column in the wikipedia table, which states the effective datarate in MByte/s for USB3.0. \$\endgroup\$
    – Janos
    Apr 15, 2020 at 13:06

2 Answers 2

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A USB 3.0 hub will NOT help to manage your multiple USB 2.0 cameras. Because the cameras will connect to USB 2.0 section of the hub, and there is only one USB 2.0 link upstream. So your total throughput will be still limited to a single 480 Mbps raw speed, and you can't get more than 280 practical Mbits/sec from it, Why are USB devices slower than 480 MBit/s.

Your best bet to handle several USB 2.0 cameras is to use a host with multiple USB 3.0 ports, and dedicate each port to separate camera. The ports can be connected to several on-board controllers, or be from the same one. See related considerations here. With some caveats as usual.

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From this book USB Complete

A USB 3.0 hub contains both a USB 2.0 hub and a SuperSpeed hub and handles traffic at any speed. SuperSpeed traffic uses the SuperSpeed hub’s circuits and wires, and other traffic uses the USB 2.0 hub’s circuits and wires.

enter image description here

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  • \$\begingroup\$ Thank you for your answer @Emir Sehic. I really couldn't decide which answer to 'accept' and I would have liked to be able to accept bot. Both are really helpful to me. \$\endgroup\$
    – Janos
    Apr 15, 2020 at 13:07

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