Re: High Power USB hub port...


"SMS" <scharf.steven@xxxxxxxxxxx> wrote in message
news:46d61b1b$0$27165$742ec2ed@xxxxxxxxxxxxxxxxx
Al Gillis wrote:
Family pressures were brought to bear on me yesterday and I had to go to
Costco. So, to do my part to keep America and China strong I bought a
SanDisk 2 gigabyte flash drive.

The specs on this gizmo claim to need a "high power USB hub port". So I
looked briefly at Dell dot com but couldn't learn if my Precision M-60 or
my Inspiron 1705 has such a port.

Can you please help me? Point me to a reference on the Dell site or on
the USB.org site? Or explain that the wording "hub port" means I need an
external hub to run this gizmo? (I'll go look at sandisk.com as well).

Thanks in advance!

It needs a port that is capable of providing the full 500mA. Any USB port
on the computer will be fine as each USB port can provide a minimum of
500mA.

That is not actually quite correct. The USB spec requires a port to supply
a minimum current of 100 mA. Anything larger is entirely by negotiation
with the host and will only be available if the power supply can support it
once the other loads are accounted for. In general terms, this usually
means that USB ports on desktop machines can deliver 500 mA. Also ports on
self powered hubs can generally deliver 500 mA. However, ports on non
powered hubs are usually limited to 100 mA. Some laptops also limit the
current on their ports to 100 mA.

Also note that according to the USB spec., 500 mA is specified as a maximum
not a minimum. Although most ports will, in practice, deliver a bit more
than 500 mA, they shouldn't deliver much more before the overcurrent
protection kicks in. Any port designed to deliver more than 500 mA (and I
know that do exist) are strictly non-compliant.


.

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