LaCie Skwarim
Troubleshooting
User Manual
page 23
TECHNICAL NOTE:
Technically, you can connect up to 127 de
vices to a single USB bus. For more than two devices, you must make
new connections using a peripheral called a “hub.” A hub, which you
hook up directly to a USB connector on your computer, usually has 4
or 7 output connections enabling you to connect the same number of
peripherals. One of the hub’s main functions is to regenerate signals
that lose part of their strength as they are transmitted via the USB
cable. By connect ing yet another hub to a connector on the existing
hub, you can then plug in a new set of peripherals and so on, up to
a maximum of 127.
You can use your USB 2.0 devices with USB 1.1 hubs, but the pe
ripherals will be limited to USB 1.1 performance levels. As USB 2.0 is
backwards compatible, you will be able to connect USB 1.1 devices
to USB 2.0 hubs; however, the USB 1.1 devices will still maintain their
normal performance levels (i.e. 12 Mb/s).
In practice, users who desire enhanced USB 2.0 throughput will
need to connect their USB 2.0 hardware on both ends of a 2.0 hub
to achieve the “highspeed” mode. On one end, a USB 2.0 compli
ant host controller resides on the host PC to man age the enumera
tion process and power management. On the other end, USB 2.0
hardware must be connected directly to the root hub or through a
USB 2.0 hub.
Some hubs have no power supply and others are selfpowered. When
you choose a hub, opt for the selfpowered variety, as they have their
own AC adapter. The most powerful hubs provide 0.5A of power to
each port. If you buy a hub, make sure that it supports perport switch
ing. This function prevents the entire chain of peripherals from freezing
up if one of them is not working properly or is down.
IMPORTANT NOTE:
Avoid using USB connectors found on cer
tain peripherals such as keyboards. These are passive (or pass
through) connectors that lead to power loss and unstable operation.
IMPORTANT NOTE:
Only use USB cables shorter than 5 meters
(approximately 15 feet). Using longer cables cause the peripher
als to malfunction due to excessive reduction in electrical signal
strength.
