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#1
USB controller and hub weirdness, which driver handles which port
I didn't know whether to put this in General, or Hardware, or Drivers, or what. But here goes.
This particular system has Windows 7 Ultimate 32-bit, with an Abit KN9 Ultra motherboard. I was having some USB issues (a particular external USB drive wouldn't work when plugged into the front USB ports) so I started some investigating.
I thought that the built-in USB ports on a motherboard (on the back of the computer) are connected to a particular USB hub which is handled by a specific USB driver. But that doesn't appear to be true!
This is strange: When my Microsoft optical mouse is plugged into a particular port on the back of the computer, Device Manager says this when viewed by connection:
Standard OpenHCD USB Host Controller
USB Root Hub
Microsoft Hardware USB Mouse
Microsoft USB Comfort Optical Mouse 1000
(Those are indented to indicate "child" devices)
That would indicate that this particular USB port is a low-speed USB port, which worried me. BUT, if I unplug the mouse, and plug the printer in to the port that the mouse was connected to, I see this in Device Manager:
Standard Enhanced PCI to USB Controller
USB Composite Device
Canon MF4320-4350
(Those are indented too)
...which means that the SAME physical USB port is now a USB 2.0 port (Enhanced).
How can the same USB port be driven by Standard OpenHCD USB Host Controller driver one minute, and Standard Enhanced PCI to USB Host Controller the next minute? If that's how things are done these days, that's fine, but I never knew this. And the behavior was clouding my investigations -- I was convinced that the USB headers on the motherboard were not USB 2.0 (even though the documentation says they are, and Windows never complains that devices "could" perform faster if plugged into a high-speed port, etc.).
I thought that a physical USB port was connected to an on-motherboard set of circuitry that is handled by ONE driver, but apparently Windows moves drivers around when it wants to. Is this commonly known? Am I crazy? Does this happen to other people?
Thanks.
David