Do PCIe cards for USB ports with fully independent root/controllers/bandwidths exist? Alternatively, is it impossible for PCIe to pass multiple USB streams? Or is there a way to check before buying?
An example of what I'd expect to see is "Device Manager" show separate independent USB controllers?
This is for multiple reading cheap USB webcams on Windows 11, but even thunderbolt 4 and USB 3.2 can't read them together...
Yes. I’ve personally used these two cards for this purpose (multiple USB webcams), albeit in Ubuntu not Windows. Both are 4-port, 4-controller cards.
Keep in mind that most USB webcams are USB 2.0; because of the way that USB is designed, any USB 2.0 devices will still be sharing only 480 Mb/s per port, not the full USB 3.x bandwidth (i.e. there aren’t any spec-compliant USB 3.x -> 2.0 hubs that can split the 5+ Mb/s into multiple 480 Mb/s ports.)
I've confirmed StarTech PEXUSB3S44V solves the problem on Windows 11, and am accepting JMY1000's as the answer. His personal experience, actionable recommendationssolved the problem (and quickly!), and explanations about the USB (and their "gotchas") limit expectations.
John Smith's answer deserves an honourable mention for answered "what to check for before buying" and proposing an alternative (PCI-E splitters) I wasn't aware of, but didn't match the (accidental, but trick) question.
I should have explicitly stated the USB hubs all failed, despite very, very low bandwidth cameras. I tried in C#, C++, and MATLAB, and on 2 computers, and the order the capture-objects were created always mattered. The first opened on a USB hub would work, but rest failed. The order of ports didn't matter.
I suspect each camera monopolizes a controller because the camera details & controls are unavailable, so the computer defaulted to the maximum bandwidth.
I was incredulous 4 cameras might need 4 PCIe cards/slots, each with 1 controller and 3-7 unused ports, and am very glad this works. It's interesting it needs a PCI-Ex4 and dedicated power cable. Imagining a 16 camera system makes me laugh a little.
Yeah, something like the Vantec UGT-PCE430-4C -it's pricey though.
You can get cheaper as I doubt you'll need all that bandwidth. Just look for "dedicated controller".
Alternatively, if you have a big case, and space, you could get a "pcie splitter" and run multiple usb cards off it.
But if you're just plugging in cameras, then just get a decent USB-C hub, or a usb to hdmi adaptor like an OBSBOT UVC to HDMI Adapter. Depends how many cameras you're plugging in.
