Solving Usb Problems - Compaq Armada 7800 6266 T 5000 D M 1 Maintenance And Service Manual

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Solving USB Problems

Problem
External device connected to
a USB connector does
not work.
External device connected to a
USB connector does not work
during startup (before
Windows 95 loads).
External devices in lower tiers
do not work.
2-38 Troubleshooting
Table 2-29
Solving USB Problems
Probable Cause
The operating system limits
external devices connected by
USB to two tiers that 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
connector. 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.
Recommended Action(s)
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 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.