Re: [gentoo-user] Does USB devices share bandwidth?

[Caster]

On 6/22/06, 张|武 <zhangweiwu@××××××.com> wrote:
>
> Hello. My old sparc server have a USB extension card, which provides two
> USB slots at the back of the machine, driving a USB printer on Slot A.
> This printer runs at heavy load. because it cannot print the documents
> as fast as we need, I wish to add another printer. In most casese, we
> need the two printer working together the same time rather then one
> after the other.
>
> The two USB slots provided by the USB card are both OHCI (some USB 1.x
> stuff, not USB 2.0). So far it seems one single printer uses up all the
> USB bandwidth (sometimes printer stop there several seconds wait for
> signal). What would happen if I put another Printer there?
>
> case A: the new printer uses the bandwidth on slot B, both run as fast
> as if they were the only USB printer;
> case B: the new printer share bandwidth with the old one, the result is
> both printer work 1/2 fast, that is equal to not having bought another
> printer at all.
>
> Which one is true?
>
> Thanks in advance:)
>
> --
> gentoo-user@g.o mailing list
>
>

According to http://www.sounddevices.com/tech/usbbasics.htm if the ports are
on the same controller, they share bandwith. It probably depends on the
hardware if it provides controller for each port or not. I think mostly it's
two ports per controller, but dunno how to determine it... From lspci, and
lsusb I would think that in my case (nforce4ultra) it's only one controller,
but to share 10 ports ? Nonsense. In windows it shows 5 devices, which would
correspond with the idea of 2 ports per controller... but dunno how to see
that in linux.
You could probably plug some usb flash storage in and perform transfers to
see if it slows down the printing, to be sure :)

Caster