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Computers don't make sense
Sunday, January 4th, 2009 02:37 pmI thought I had figured out how to interpret the USB entries in the Device Manager.
The "Universal Serial Bus controllers" section of the Device Manager includes 2 types of entries - "USB *** Host Controller" and "USB Root Hub". There may be multiples of each listed.
When you display the Properties Window for a "USB Root Hub" and look at the "Power" tab, it shows how many ports are available on that hub, how much power is available for each port, and which devices, if any, are plugged into the ports as well as how much power they are using.
Also on the Properties window of the USB Root Hub, if you look at the "Details" tab, and select "Hardware Ids" from the dropdown, one of the things shown is a "PID" number. This number seems to indicate which "USB *** Host Controller" entry in the Device Manager that this USB Root Hub corresponds to. (Each "USB *** Host Controller" entry has a number at the end of it, which corresponds to a PID number.)
My computer has 2 USB ports in the back. The Device Manager displays 2 "USB Universal Host Controller" entries, and 2 "USB Root Hub" entries. However, each USB Root Hub entry indicates that it has 2 ports. When I have something plugged into both of my USB ports, they are both shown within the same USB Root Hub entry, and the other USB Root Hub entry displays as unused. After looking at my motherboard manual and some photos I had previously taken of the inside of my computer, I determined that my motherboard has 2 extra USB ports available, which may have been intended to connect to ports on the front of the case, but since my case does not have any front ports, they simply are not connected to anything!
Q's computer has 2 USB ports in front, and 4 in back.
His Device Manager has 5 "USB Root Hub" entries, 4 "USB Universal Host Controller" entries (this indicates USB1), and 1 "USB2 Enhanced Host Controller" (this indicates USB2).
I wanted to figure out which of his 6 physical ports are USB2 and which are USB1.
However, this is where it doesn't make sense....
The 4 "USB Root Hub" entries corresponding to the USB1 Controllers each have 2 ports listed as available.
The single "USB Root Hub" entry corresponding to the USB2 Controller has 8 ports listed as available (!).
That would mean a total of 16 ports, but there are only 6 physical ports.
No matter which physical port I plug the USB mouse cable into, it ends up displayed as connected to one of the USB Root Hubs which has a USB1 controller.
No matter which physical port I plug the USB wireless adapter into, it ends up displayed as connected to the USB Root Hub which has a USB2 controller. The same thing happens for a flash drive I was testing with.
So, for the same physical port, depending what device I plug into it, the device ends up being displayed in different "USB Root Hub"s.
So I guess the USB Root Hubs do not necessarily correspond to the physical ports after all.
The "Universal Serial Bus controllers" section of the Device Manager includes 2 types of entries - "USB *** Host Controller" and "USB Root Hub". There may be multiples of each listed.
When you display the Properties Window for a "USB Root Hub" and look at the "Power" tab, it shows how many ports are available on that hub, how much power is available for each port, and which devices, if any, are plugged into the ports as well as how much power they are using.
Also on the Properties window of the USB Root Hub, if you look at the "Details" tab, and select "Hardware Ids" from the dropdown, one of the things shown is a "PID" number. This number seems to indicate which "USB *** Host Controller" entry in the Device Manager that this USB Root Hub corresponds to. (Each "USB *** Host Controller" entry has a number at the end of it, which corresponds to a PID number.)
My computer has 2 USB ports in the back. The Device Manager displays 2 "USB Universal Host Controller" entries, and 2 "USB Root Hub" entries. However, each USB Root Hub entry indicates that it has 2 ports. When I have something plugged into both of my USB ports, they are both shown within the same USB Root Hub entry, and the other USB Root Hub entry displays as unused. After looking at my motherboard manual and some photos I had previously taken of the inside of my computer, I determined that my motherboard has 2 extra USB ports available, which may have been intended to connect to ports on the front of the case, but since my case does not have any front ports, they simply are not connected to anything!
Q's computer has 2 USB ports in front, and 4 in back.
His Device Manager has 5 "USB Root Hub" entries, 4 "USB Universal Host Controller" entries (this indicates USB1), and 1 "USB2 Enhanced Host Controller" (this indicates USB2).
I wanted to figure out which of his 6 physical ports are USB2 and which are USB1.
However, this is where it doesn't make sense....
The 4 "USB Root Hub" entries corresponding to the USB1 Controllers each have 2 ports listed as available.
The single "USB Root Hub" entry corresponding to the USB2 Controller has 8 ports listed as available (!).
That would mean a total of 16 ports, but there are only 6 physical ports.
No matter which physical port I plug the USB mouse cable into, it ends up displayed as connected to one of the USB Root Hubs which has a USB1 controller.
No matter which physical port I plug the USB wireless adapter into, it ends up displayed as connected to the USB Root Hub which has a USB2 controller. The same thing happens for a flash drive I was testing with.
So, for the same physical port, depending what device I plug into it, the device ends up being displayed in different "USB Root Hub"s.
So I guess the USB Root Hubs do not necessarily correspond to the physical ports after all.
