On Sat, Dec 15, 2018 at 10:55:49AM -0500, Alan Stern wrote: > > Does it mean that I should indeed have 2 separate USB controllers for > > USB-2 if I know where to tap and therefore should have a 64 device limit > > if I spread the load? > > EHCI is not subject to the 32-device limit of xHCI. A single EHCI > controller can handle up to 126 devices. But of course, EHCI only > supports high speed (480 Mb/s), not SuperSpeed (>= 5000 Mb/s). Ok, this is maybe my salvation. I'm connecting fdti adapters (i.e. usb to very slow serial) and fastboot (android flashing protocol) which doesn't need to be super fast either. I'm using fancy USB3 hubs for which I've replaced the cables with USB2 cables to force the speed down to USB2/EHCI. So the thing is that I think I'm already doing that you're saying since I'm forcing the speed down with the USB2 cable. Should I be using a USB2 HUB or even a USB1 hub to reduce the number of endpoints per device further? Re-reading https://acroname.com/blog/why-cant-i-connect-more-usb-30-devices-my-system it says "Each individual USB device consumes 3 USB endpoints: one endpoint for bulk transfers, one for isochronous transfers and one for control." and "Many modern USB 3.0 hosts use Intel XHCI USB controllers, which impose their own limit on the total number of endpoints to 96" and "If you need to add more than 18 total devices to your XHCI system and you do not need USB 3.0 performance, the simplest solution is to use a USB 2.0 host cable to connect your host to USBHub3+. Since the USBHub3+ is now connected only with USB 2.0, there will not be any enumeration of USB 3.0 devices, including the USB 3.0 hub chips internal to USBHub3+. This will effectively reduce the USBHub3+ footprint in your USB tree from 6 devices to 3 devices." I'm already doing the USB2 cable trick, but I don't think it's saving me that many device slots, maybe just 2 or 3 like the last paragraph says? > > Right, but my 1U servers only allow a single PCI card. Is there even > > such a thing as a PCI(e) card that has multiple USB host controllers? > > Clearly the one I bought only has a single. > > > 05:00.0 USB controller: Fresco Logic FL1100 USB 3.0 Host Controller (rev 10) > Yes, there are such cards. But whether you can find one with multiple > USB-3 controllers is a different question. I don't need multiple USB3 controllers, multiple USB2 controllers woulud be fine, but that's probably even harder to find since I'd have to buy one from 15y+ ago? Mar -- "A mouse is a device used to point at the xterm you want to type in" - A.S.R. Microsoft is to operating systems .... .... what McDonalds is to gourmet cooking Home page: http://marc.merlins.org/ | PGP 7F55D5F27AAF9D08
