User Guide

2-26 Troubleshooting
Table 2-19
Solving USB Problems
Problem Possible Cause Solution
External device connected to
a USB connector does not
work.
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.
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.
External device connected to
USB connector does not
work during startup (before
Windows 95 loads).
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.
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.
External devices in lower
tiers do not work.
An unpowered hub is
connected to another
unpowered hub.
Use only powered hubs.
Make sure that all unpowered
hubs are immediately preceded
by powered hubs in the USB
chain.