Compaq Armada M700 Series Maintenance And Service Manual page 56

Problem
External device connected
to a USB connector does
not work.
External device connected
to USB connector does not
work during startup (before
Windows 95 loads).
External devices in lower
tiers do not work.
Table 2-19
Solving USB Problems
Possible Cause
The operating system limits
external devices connected
by USB to two tiers which
can include no more than
two hubs on the first tier and
no more than one keyboard
and one pointing device on
the first or second tier.
During startup, only two tiers
are supported by the USB
port. These tiers can include
no more than two hubs on
the first tier and no more
than one keyboard and one
pointing device on the first
or second tier.
An unpowered hub is
connected to another
unpowered hub.
Solution
Reduce the number of connected
external USB devices to no more
than two hubs on the first tier, and
no more than one keyboard and
one pointing device on the first or
second tier.
Use the external device only after
Windows 95 or Windows 98 has
loaded.
Reduce the number of connected
external USB devices to no more
than two hubs on the first tier, and
no more than one keyboard and
one pointing device on the first or
second tier.
Use only powered hubs.
Make sure that all unpowered
hubs are immediately preceded
by powered hubs in the USB
chain.
Troubleshooting 2-25