"Yousuf Khan" <bbbl67@[EMAIL PROTECTED]
> wrote in message
news:ipSdnROWzJM6I-vaRVn_vwA@[EMAIL PROTECTED]
>I have two generic 4-****t USB hubs that are supposed to be USB 2.0
>compliant. The older one is fine, works as advertised. Meanwhile the
>newer one sometimes shows up under the USB 2.0 root hub (i.e.
>"Standard Enhanced PCI to USB Host Controller"), or usually it shows
>up under the slower "Standard OpenHCD USB Host Controller" (USB 1.1).
>
> My motherboard (Asus M2NPV-VM) USB ****ts are all USB 2.0 compliant,
> and they individually auto-detect whether they need to switch down
> to USB 1.1 speeds. I'm using a Microsoft tool called UVCView under
> Windows XP to display the details of the USB devices, including the
> hubs and roothubs.
>
> According to UVCView, the older hub and newer hub seem to have the
> same chipset vendor (idVendor = "Genesys Logic, Inc."), although
> externally they look quite different and have different brand names.
> So I'm not sure why one would be consistently USB 2.0 compliant,
> while the other one is not.
>
> Now another interesting thing I noticed is that the inconsistent hub
> will only show up as USB 2.0-compliant after I boot into Windows
> after having previously rebooted from Ubuntu 7.10 Linux (dual-boot
> system). So maybe Linux does something to the device that puts it
> right. But when I list the devices while in Linux I see that it is
> listed under USB 1.1 just like when in Windows. I have no idea why
> Linux leaves the hub fixed for Windows, but doesn't fix it for
> itself?!
>
> Any idea what's going on with this hub?
>
> Yousuf Khan
Have you visited the manufacturer's web site to get the specs on those
USB hubs? Having the same hardware (i.e., chipset) says nothing about
how the manufacturer utilized that hardware. Lots of analog modems
use the same Conexant chip but the *cards* don't have the same feature
set. Same subsystem components do not enforce the same system
features. Could be one of the hubs really only is 1.1 compliant and
that using it as a 2.0 device is not recommended. Of course, the
device could be just a crappy low-grade cheap unit that doesn't
properly respond to re****t itself correctly, or you need a better USB
cable.
Are both of these a self-powered hub (i.e., they have a power adapter)
or a low-power hub that relies on the current supplied from the USB
controller at the motherboard? If they are bus-powered hubs, they
CANNOT be on the same USB controller. Each controller provides 2
****ts (channels) but these 2 ****ts still share the same controller and
so both are limited by a total amperage that can be supplied by the
same controller. That's why you see USB ****ts in pairs but you have
to watch how much current is drained by them together. Bus-powered
hubs or any other bus-powered devices will tax the low current
available from the USB controller, so instead make sure to use
self-powered USB hubs, especially considering that you are planning to
connect more than just 2 USB devices to the same controller (and
possibly not just low-powered USB devices). Initially a USB device is
allowed to draw 100 mA but that device may request more power for
upstream devices in increments of 2 mA but up to a maximum of 500 mA
(and that is across the pair of ****ts to the same USB controller).
For a bus-powered hub, the connected devices may only use a total of
400 mA (100 mA per ****t) so the hub is limited to 4 ****ts. If using
bus-powered hubs, make sure you are using low-power USB devices (or
the high-powered USB device provides its own power supply that is
connected to a bus-powered hub). USB devices rated for bus-power draw
can be used on a bus-powered hub (but watch the total draw across both
USB ****ts to the same controller). The number of bus-powered or
high-power devices that you connect to a self-powered hub depends on
how much current that hub can deliver.
USB devices are supposed to re****t their power consumption. Maybe you
hubs don't. Or maybe they re****t too high a consumption to guarantee
USB 2.0 mode to work so the controller degrades to USB 1.1 mode.
Do you actually have any high-speed USB 2.0 devices connected to the
hubs when you boot the OS with the self-powered hubs already powered
up? Are they really high-speed USB 2.0 devices (USB 2.0 compliant
devices can re****t as low, full, or high-speed)?
For best setup, use self-powered hubs, or connect them to different
USB controllers (i.e., they don't share the same ****t pair coming from
the same USB controller).
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