Typically, if you plug a
malfunctioning or
incorrectly-configured
device into a USB port,
it causes the computer
to stop responding
(hang). In the majority
of these instances, you
must physically turn off
the computer and turn it
back on to reset the
bus. Note that it may be
more difficult to
identify which device is
malfunctioning or is
incorrectly configured.
If another computer that
you know is working
correctly is available,
try to plug the device
into that computer to
see if you encounter the
same issue.
If the device is plugged
into a secondary hub,
unplug the device from
the hub, and then plug
the device directly into
the root hub.
Many hardware problems
(such as high or low
power, bandwidth
shortage, malfunctioning
or incorrectly
configured firmware, and
so on) can cause issues
to occur.
Check Device Manager to
be certain that the root
hub is functioning
correctly. If the root
hub is displayed with an
exclamation point (!) in
a yellow circle, verify
that the BIOS is
assigning an interrupt
request (IRQ) to the
root USB controller.
This is required for the
device driver to be
loaded. For additional
information about how to
use Device Manager to
troubleshoot hardware
issues, click the
article number below to
view the article in the
Microsoft Knowledge
Base:
133240
(http://support.microsoft.com/kb/133240/EN-US/)
Troubleshooting
Device Conflicts
with Device Manager
If no devices work when
you plug the devices
into the root hub,
verify that the power
requirements of the bus
are not being exceeded.
USB devices can draw a
maximum of 500 milliamps
for each connection. If
a device attempts to
draw more power than
this, the specification
recommends that the
computer should be able
to disable that specific
port until the computer
power is cycled (this is
called "suspending" the
port). In addition, if
the device draws less
than 50 milliamps, the
port never becomes
active.
Check the
Power tab
in USB Root Hub
properties to check the
power usage of the USB
bus.
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