XP's incorrect USB hub report

[kimiraikkonen]

Hello,
XP Pro SP2 and have no problems recognizing hubs, but i know / i'm
sure as stated in my motherboard's user manual, i have 3 hubs x 2
ports each = total 6 USB ports (USB 2.0)

But in device manager it reports 4 USB root hubs and under "power" tab
power requirement of device is reported sometimes wrong. For example
one day it shows my flash drive requires 200mA to operate, some day it
says 100mA is enough. Also at the last root hub(forth one) it says i
have 6 ports free (but still usb optical mouse is operating).

I'm not quite sure but in device mangager hubs and power requirement
report is wrong as i tested.

Any comments?

Thanks.

 

[R. McCarty]

Motherboards have BOTH Enhanced ( USB2 ) and Full Speed
( USB1.1 ) controllers and Root Hubs. There are more USB 1.1
Controllers because USB connections are internally routed. When
you plug a USB 2.0 peripheral in the routing connects it to the USB
2.0 Controller/Root Hub. To create an equivalent number of ports
( visualize sockets ) there must be more USB-1.1 controllers and
Hubs. These are hard wired to specific sockets.

Recent motherboards now provide more than a single Enhanced
USB controller.

 

[kimiraikkonen]

Yes i have 3 usb 1.1 and a (one) usb 2.0 controller = totally 6 ports.

When i plug a usb 2.0 hi-speed device XP does not complain if device
is OK, but power requirement decreases sometimes, sometimes increases
for the same device.

Additionaly, amount of USB ports which are reported under "usb root
hub" is frustrating. Could you clarify which number is OK?

For example my friend has a 3 year-old notebook with only 2 ports but
there are 4 usb root hubs reported under "device manager".

Why?

 

[R. McCarty]

Never experienced variable mA draws using the same device.
On my system the peripherals maintain a constant current.

Notebooks have chipsets that can provide more ports than the vendor
actually chooses to provide physical ports/sockets.

Best tool for examining USB device trees is UVCView:
http://www.microsoft.com/whdc/device/stream/vidcap/UVCViewdwn.mspx?

 

[RalfG]

The number of hubs and ports being reported isn't a problem. They represent
the capability of the USB controller chipsets (2x 8 = 16 ports), not the 6
physical USB connectors provided to you on the computer. The specifications
in the owners's manual represent what you paid for, not the maximum
capability of the USB chipset. Windows reports what the installed USB1/2
chipset capacity (electronic) for connections is, not the physical ports
(wiring) that were provided on the computer

The USB 2 controller connects to 1 root hub that can operate 8 directly
connected ports, although you only have 6 physical ports attached to it.
There are 4 USB 1.1 controllers which operate 1 root hub each, with 2 ports
each. Again only the same 6 physical ports are connected to the USB 1.1
controllers as the USB 2 controller. Obviously you can increase the number
of physical ports by attaching external USB hubs to any of the existing
ports. Since the same physical ports are connected to both USB 1.1 and USB
2 controllers the type of USB device that you attach to the port will
determine whether that port will connect (electronically) to either a USB
1.1 or USB 2 root hub. Example, an external USB2 hub attached to any of the
ports will show up as being attached to the USB2 root hub and controller. A
USB 1.1 hub attached to that same port will show up as being connected
through a USB 1.1 root hub to one of the USB 1.1 controllers.

If you have a memory card reader in the computer it would also be connected
through one of those 4 USB 1.1 controllers.