Tech: USB 'malfunction' solution

Subject: Tech: USB 'malfunction' solution
From: Bernard
Date: 21 Oct 07 - 07:54 PM

A bit odd, this one, so I'm posting it in case anyone else has had the problem...

My main PC (this one) is rarely switched off, just restarted occasionally after some updates, and I have a couple of USB hubs attached.

Last week I had a message bubble to say a USB device had malfunctioned, and it turned out to be one of the hubs (USB 2) which was returning the message. I temporarily replaced it with an old USB 1,1 hub, which worked fine...

As the 'failed' hub has been plugged in constantly for some years, I decided to go and buy a replacedment... which gave me the same message!

So I naturally figured that maybe neither of them was faulty, and it was a problem with the USB port hardware or driver... rather than wade in with both feet and wreck everything, I trawled around the net for a while, and found out that it's a known issue with USB 2 ports.

Most people advised that I should uninstall the USB drivers, restart in 'Safe Mode' and delete all the driver files... which seems rather drastic, although I have had to do similar things with dodgy video drivers and such.

One glimmer of hope, which seemed too good to be true, was a suggestion that the port controller chip had crashed, and that I simply needed to shut the PC down and unplug the power cord for a minute or so.

I duly did this, and... IT WORKED! The old hub is now happily sitting in its customary place, and working just as well as before!

Nobody was more surprised than me...!

Hopefully this will be of help to others. The reason why a restart didn't clear the fault? Most motherboards these days need the 5v rail (which also powers the USB ports) to enable the software 'power switch' to operate - which is one reason why you should always pull the power cord out before changing memory chips, CPU etc. As the 5v was keeping the USB chips 'live', they did not get a 'cold reboot'... so they wouldn't function in USB 2 mode, yet still worked in USB 1.1 mode!

Hah!

Subject: RE: Tech: USB 'malfunction' solution
From: Midchuck
Date: 21 Oct 07 - 08:55 PM

Irritating thing about my laptop. You need to do a cold reboot, you have to open the back and take the battery out.

Things should have an "off all the way" switch.

Peter

Subject: RE: Tech: USB 'malfunction' solution
From: JohnInKansas
Date: 21 Oct 07 - 10:33 PM

Since the 5v rail in most computers is fairly limited in capacity, quite a few USB hubs have their own wall wart to supply power for the hub, and to power any USB devices that feed off of them.

With "separately powered" hubs, you may need to unplug the hub power (in addition to full power off for the computer) to get a full reset of the hub.

It's handy to have a single (or few) multi-tap power strip(s) that all of the warts plug into, so that with the computer down, one switch can cycle them all off and back on.

If you actually use more than 2 or 3 USB devices (at the same time), you probably should have a powered hub, since the stuff you plug into the hub otherwise can overload the computer's 5v line. "Passive" hubs, that use computer power only, are fine if they're just for things like the camera that you plug in only during downloads, etc, where it's just a matter of getting the connection point out from behind the computer, or if you just want to leave the cords with a few of those 7 "special USB connectors" in place but usually "empty" to plug the camera, videocam, etc in for downloads one at a time.

John

Subject: RE: Tech: USB 'malfunction' solution
From: JohnInKansas
Date: 21 Oct 07 - 10:48 PM

Midchuck -

Most laptops are "resistant" to full shutdown, but in Windows you may find that at Start|Settings|Control Panel|Power Options you can change the setup so that a "Shutdown" option is offered. Most laptops default to use "Standby" and "Hibernate" modes that only turn off a few things, but the third choice - Shutdown - should turn off at least the connected hubs - assuming they're similar to my couple of most recent ones.

A few laptops may have a separate "green control" program that you need to find to manipulate it's brain warps, but most will respond to the Control Panel settings.

Most have a "reset" button that you can use to bring the machine out of Hibernation, and if you press and hold for a few seconds it's common for them to open the shutdown/restart dialog where you can choose a full off. Laptop builders are, unfortunately, quite "creative" about making your life difficult though, so yours may be a deviant form.

John