Thanks for your reply, and thanks for bearing with me, I'm not actually that knowledgeable on how things work with multiple USB controllers at the same time. I have a few questions I've outlined. Question #1, if I have a random computer that outputs this: Bus 002 Device 001: ID 1d6b:0003 Linux Foundation 3.0 root hub Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub Does this mean I have both an EHCI and xHCI controller? If xHCI supports USB2 also, why would it come with 2? On Sat, Dec 15, 2018 at 09:59:44PM -0500, Alan Stern wrote: > > I also read that it's difficult to unload the xhci module after it's > > been loaded because too many things use it. > > Unloading it isn't difficult at all (assuming it was built as a module > in the first place). And even if you can't unload it, you can unbind > it from the xHCI hardware, which will have much the same effect. Understood. It wasn't clear from what I had read. > > Someone suggested checking whether there is a way to turn off USB3 in my > > bios, turning off xhci support altogether. > > From what you're saying it sounds like it would fix my problem assuming > > the bios allows this at all. I'll need to check in the office next week. > > Depending on what hardware you have on your computer (something you > have not described so far in this conversation -- you haven't even > provided the output from "lsusb"), disabling xHCI support might prevent > all of the USB devices attached to the computer from working. Sorry, I pasted an incomplete lsusb, I'll get the full one tomorrow. > Second, who says you need a USB-2 only card? What you need is a card > with an EHCI controller; nothing prevents the card from having an xHCI > controller too. Question #2: I may be confused, but xHCI supports USB2, correct? If so, why would a card provide both a xHCI chip and a EHCI chip if xHCI can do both? > > > There are still old cards around, and probably there are still cards > > > being made that don't have xHCI. Regardless, even if a card does have > > > an xHCI controller, as long as it also has an EHCI controller and you > > > use only USB 2 cables, you should be okay. > > > > That's the thing though, this is exactly what I do. > > I don't think so; I strongly suspect your card does _not_ have an EHCI > controller. "this is exactly what I do" == "use only USB 2 cables" I agree with you that I don't think the card has an EHCI controller. > It's not a question of whether you use USB-2 signalling or USB-3 > signalling; it's a question of whether you use an EHCI controller or an > xHCI controller. The 32-device limit is inherent in the controller, > not in the signalling. Thanks for confirming. > > Right, that I know how to do, but finding a EHCI only PCIe or > > motherboard is going to be next to impossible. > > See above. And don't be such a pessimist: > https://www.amazon.com/Port-Express-Profile-High-Speed/dp/B002RL8V7E I'm not sure how I failed to find this, but I clearly did, thanks for the link. > If all the controllers on the motherboard and on the add-on card are > xHCI, then disabling xHCI support in the kernel will prevent any of > your USB devices from working. That isn't what you want. Point taken. I think I was thinking about USB ports that were routed to either a xHCI or an EHCI chip depending on what's plugged into them, but seems that I didn't quite understand how that worked. Thanks for your reply, Marc -- "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
