Re: USB devices fail unnecessarily on unpowered hubs

[Lennart Sorensen]

On Thu, Jun 01, 2006 at 11:09:46AM -0400, linux-os (Dick Johnson) wrote:
> Many, most, perhaps all such devices don't take more power when they
> are "enabled". Everything is already running and sucking up maximum
> current when you plug it in! If the motherboard didn't smoke when
> the device was plugged in, you might just as well let the user use
> it! Perhaps a ** WARNING ** message somewhere, but by golly, they
> got it running or else you wouldn't be able to read its parameters.

I imagine something like a harddisk might use more power while
reading/writing than when it is just spinning.  It might even start
powered down until sent some command that causes it to spin up.

A scanner certainly uses more power with the scanner light on than with
it off, and it starts out off until it is in use on most scanners.  Of
course I have never seen a usb powered scanner, so it doesn't seem to
matter.

Len Sorensen
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