usb hubs and mass storage devices

[Guest bigal1808]

I'm trying to use a mass storage device, but xp says it does not recognise

the device.

all the drivers check out ok, there's no red crosses, no yellow q. marks.

 

what 's going wrong.

 

has anybody got any ideas please.

[Guest Jerry]

Re: usb hubs and mass storage devices

 

Is the USB hub capable of providing enough power to the device plugged into

it?

 

"bigal1808" <bigal1808@discussions.microsoft.com> wrote in message

news:F1775C62-8803-420E-9321-D98873B26EF9@microsoft.com...

> I'm trying to use a mass storage device, but xp says it does not recognise

> the device.

> all the drivers check out ok, there's no red crosses, no yellow q. marks.

>

> what 's going wrong.

>

> has anybody got any ideas please.

[Guest PD43]

Re: usb hubs and mass storage devices

 

"Jerry" <ChiefZekeNoSpam@MSN.com> wrote:

>Is the USB hub capable of providing enough power to the device plugged into

>it?

 

If it has its own power supply it does. Otherwise it probably

doesn't.

[Guest Colin Barnhorst]

Re: usb hubs and mass storage devices

 

How many usb devices are attached to the computer? Even though your mass

storage device probably has its own power supply the usb bus itself may be

overloaded. Try the device without the hub. Disconnect as many usb devices

as you can while troubleshooting.

 

"bigal1808" <bigal1808@discussions.microsoft.com> wrote in message

news:F1775C62-8803-420E-9321-D98873B26EF9@microsoft.com...

> I'm trying to use a mass storage device, but xp says it does not recognise

> the device.

> all the drivers check out ok, there's no red crosses, no yellow q. marks.

>

> what 's going wrong.

>

> has anybody got any ideas please.

[Guest M.I.5¾]

Re: usb hubs and mass storage devices

 

 

"Colin Barnhorst" <c.barnhorst@comcast.net> wrote in message

news:57E789A8-1EFA-402F-B2E7-9F9B54DA7137@microsoft.com...

> How many usb devices are attached to the computer? Even though your mass

> storage device probably has its own power supply the usb bus itself may be

> overloaded. Try the device without the hub. Disconnect as many usb

> devices as you can while troubleshooting.

>

 

The USB bus system supports a total of 128 devices including the root port

and it's associated root hub. Every hub* and device counts, but there is a

limit of 5 hubs between the root port and the peripheral. The position is

complicated by the fact that a USB port on a modern PC actually connects to

one of 2 USB systems. USB1 (12 and 1.5 Mbps) peripherals and hubs connect

to one system while USB2 (400 Mbps) automatically connect to the other.

Although a USB1 system theoretically supports 128 devices, it is in fact

fairly easy to overload with just a modest handful of devices and when such

an overload occurs, there is no error message, just a device or devices that

won't work for any identifiable reason.

 

In your case you are getting a message saying that the device is not

recognised. This is usually a driver issue but can be caused by exceeding

the above limitations. First thing to try is to go into device manager and

find the actual device (it may be under unknown devices or under an obvious

heading (USB devices or disk drives) and may have a yellow '!' over it.

Right click and uninstall it. Ensure that any required drivers are

installed or available. Although not normally required for Windows XP there

are exceptions. Some drivers have to be installed before the device is

connected for the first time, others are installed after the device is

connected - check the documentation. Then connect your device to a root USB

port, ensuring that any power requirements are fully met. Once it works

here, it should work when connected anwhere alse (it will reinstall unless

it is electronically serial numbered).

 

If the device still won't install correctly, try it on another PC. It has

been known for conflicts to arise that prevent devices that otherwise should

work - not to work. These can be a PITA to resolve.

 

There is one gothcha. It sometimes happens that a second device of a

particular type won't work if an identical device is already connected.

This is due to manufacturers adopting the cheapest interpretation of the USB

specs (because of an ambiguity). There is a workaround, but I don't have it

to hand.

 

*Some hubs are actually 2 cascaded hubs, particularly if they have more than

4 downstream ports.

 

HTH.