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E-DOC-CTC-20050705-0001 v1.0
Chapter 4
Troubleshooting and Software Updates
4.3 USB Troubleshooting
Isochronous vs. bulk
mode
Whether your SpeedTouch™ will use isochronous or bulk transfer mode depends the
type of USB interface (USB bandwith), on the ADSL line rate (ADSL bandwith), and
on your provider’s configuration file.
The factory defaults are:
If the port on your computer is a USB 2.0 high-speed interface, then the
SpeedTouch™ shall use high-speed bulk mode.
If the port on your computer is a USB 1.1 full-speed interface, and if
The line rate is under 7,2 Mbps, then the SpeedTouch™ shall use full-
speed bulk mode.
The line rate is above 7,2 Mbps, then the SpeedTouch™ shall use full-
speed isochronous mode.
Warnings in
Diagnostics tool
On the USB tab in the Diagnostics tool, a yellow warning symbol will notify you on a
non-optimal configuration. Following messages are possible.
Fore more information on isochronous mode and bulk mode, see
“ Isochronous vs. bulk mode” on page 22.
Warning Explanation Solution
Your SpeedTouch™ can
perform faster if you
connect it to a high-
speed USB 2.0 port.
The Diagnostics tool
detected that you are
using a USB 1.1 interface
port on your computer.
To get the speeds you
pay for, upgrade your
computer port to USB
2.0.
Your SpeedTouch™ is not
able to use isochronous
mode. Try to remove
other USB devices.
The Diagnostics tool
detected that you are
using a USB 1.1 interface
port on your computer
and that several devices
are attached to this
interface. The
competition for
bandwith will result in
lower performance.
Disconnect the other
devices or put the other
devices in bulk mode if
possible.
The best course of action
is to upgrade your
computer port to USB
2.0.
Your SpeedTouch™ is
using USB bulk data
transfer. Your data
performance might be
low or erratic.
The Diagnostics tool
detected that you are
using a USB 1.1 interface
port on your computer
and your line rate is over
12 Mbps (ADSL
bandwith > maximum
full-speed USB 1.1
bandwith).
Try to make sure to use
only one device, being
the SpeedTouch™.
The best course of action
is to upgrade your
computer port to USB
2.0.
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