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#1
understanding USB port, USB hub, Host controller architecture
Lenovo B570 (laptop)
Win7 HP, x64 SP1
I am not experiencing any problems. I am just trying to figure out how things work. I am exploring the relationships of the Host Controller, Root Hub, and USB Ports. Any helpful insight would be appreciated.
This computer has four USB ports. I plugged the following devices into the USB ports:
- Logitech Unifying device for wireless mouse/keyboard combo
- Logitech dongle for wireless headset
- external hard drive
- another external hard drive
Then I explored Device Manager > Universal Serial Bus controllers in all of the following categories (two instances of each):
- Generic USB Hub
- Standard Enhanced PCI to USB Host Controller
- USB Composite Device
- USB Root Hub
The properties revealed seven (7) distinctly different port#/hub# combinations. With the four devices plugged into the USB ports, these four devices were self explanatory.
Another device was identified as my finger print reader. (which I have disabled) I am trying to figure out if the finger print reader is hard wired to either the Root Hub or the Host Controller, or if it is a virtual connection made through the registry.
The remaining two connections remain a mystery to me. I may not have known how to access the information to identify them. I do, however, have a virtual machine installed. The VM was not running at the time when I explored Device Manager. I also have a built in web cam which I did not load drivers for when I performed a clean install. Is it probable that these two devices are the ones I could not identify, or is there a more likely explanation?
While I am at it, I would like to know if my understanding of the architecture is correct. Here is the way I understand it. All physical USB ports connect to the Root Hub. I don't know if there are virtual connections to the Root Hub also. The Host Controller handles all data from the Root Hub by breaking it down in a manner similar to sending email in packets. Depending on activity, the data may be sequential from a port or a combination of packets from multiple ports which are reassembled into complete data transfers at the CPU. Is this somewhere close to how it works?
Thanks for your replies.
drpepper