USB clash

  Tycho 16:23 09 Aug 2005

I have USB 1 using an Intel 82371AB/EB PCI to USB Universal Host

Controller in a W2K computer.

I have the following devices pluggged into the 2 usb ports on

the back of the computer: A cradle for my iPAQ PDA aand a 4 port

hub on a 0.5m extension. Plugged into the 4 port hub is an ECS

4 slot card reader on a 2m extension and a Speed Touch ADSL

modem. All works well until I plug in the USB lead to the

printer. When I do this the computer reports that a device has

been illegally unplugged and the modem stops working.

The combination which causes the problem is Modem, Card reader

and printer. Remove any one of those and all is well.

Is there anything that I can do to get these three workin



  scotty 16:54 09 Aug 2005

Do you have a separate power supply for the USB hub? If not, you are possible putting too much load on the supply from the pc.

  Graham ® 17:07 09 Aug 2005

I would advise fitting an additional USB PCI card, and use it exclusively for the ADSL modem - they use the full 500mA normally available.

  Tycho 17:13 09 Aug 2005

That had occurred to me. No I am using the power that comes from the port.

On the device manager the USB root hub reports a total of 2mA and the generic hub reports a total of 600mA.


  Tycho 17:18 09 Aug 2005

It looks as if I am over this limit, then. Can I fit a USB 2 board on this old computer? (Pentium II, 400MHz, 328MB RAM (or something like that!)).

This does not seem to be the problem though because it is the printer that upsets it and that takes no current from the port but my flash drive does not upset it and that takes a further 200mA.

At the moment I am dawing about 800mA from the USB port and it is still functioning properly but if I plug the printer in it all goes to pot!


  Graham ® 17:31 09 Aug 2005

Should be OK: click here

  Tycho 17:43 09 Aug 2005

Thaks for the link. I may follow that up later but until I get this particular clsh ironed out I will leave it as it is.

Can I do any permanent damage by overloading the USB port?


  Graham ® 17:43 09 Aug 2005

Can't link directly! Item 32620 is the sort of thing you need.

  Graham ® 17:44 09 Aug 2005

You will create a lot of error reports!

  woodchip 18:13 09 Aug 2005

Yes you can blow a Onboard Fuse for the USB and there is no way of replacing it

  jack 18:20 09 Aug 2005

The joy of USB is that it is hot swappable-
Therefore if it is not in use -leave it unplugged.
except that is for the printer. These usually set themselves up with a 'printer support' USB which is separate.
As discussed the more 'bare' USB devices plugged in the more the 'pull' on the PSU, thus slowing or completely stalling the machine.
A self powered hub is a remedy.

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