USB Diagnostics

Don Bradbury takes a look at what Windows ME can do to troubleshoot USB

Diagnosing problems arising from USB installations is better provided for than in most other areas of computing. That's as it should be because Intel has been developing USB for several years now. Working hand in glove, as they do, with Microsoft, you'd probably expect a little help from the Operating System when problems become evident with this most useful connectivity medium.

Yes, problems can and do arise, and not just with USB peripherals themselves; the host controllers can 'throw up their hands', too. But, fortunately, Windows' Device Manager (Start / Settings / Control Panel / System / Device Manager) offers assistance when issues such as bandwidth and power consumption come to the fore.

Standards

But first, from the top, let's consider standards. The two standards for USB host controllers are Universal Host Controller Interface (UHCI), and Open Host Controller Interface (OHCI). The first is proprietary to Intel Corp, while the second is, as its name suggests, an open standard, a creation of Compaq, Microsoft, and National Semiconductor.

OHCI will probably be found in association with non-Intel chipsets (eg VIA, Ali, and SiS). Incompatibilities with peripherals intended for use with the alternative standard can become apparent, and you might be faced with the prospect of having to ignore your system ports and install an add-on card into your PCI bus in order to accommodate your device, the card operating with the correct host control standard.

Drivers and BIOS

Always make sure you have the chip manufacturer's own drivers installed, and bringing your BIOS specification up to date is also a useful move.

You can easily check which controller your system is using by going into Device Manager, expanding the USB Controllers line, and checking for any exclamation marks - which would indicate trouble. The Host Controller and the Root Hub should be there at least, and any add-on hubs you have, or additional controllers. The individual USB devices themselves will be listed under their own headings, of course.

Useful information concerning the USB bus can be extracted here. Look first at the Properties on the host controller's Advanced tab. Bandwidth sharing can be seen; that is, the manner in which available bandwidth is distributed among the attached peripherals. Remember that the controller itself demands about 10% of the available bandwidth.

If power consumption appears to be your difficulty, point to the root hub, select Properties, and open the Power tab. First, that will tell you if your hub is self-powered or not and the current it can deliver. If it isn't self-powered, it should be. A bus-powered hub will soon run out of current capacity, so multiple ports on the hub will be all but useless if you're in the habit of running power consumers such as scanners from these ports.

But you can also see the power consumed by each individual item of USB gear on the hub, and that's useful if any are seen to exceed or approach the maximum of 500mA. That's the specification rating for a USB port, whether main system hub (on the system box) or a secondary hub.

Non-self-powered secondary hubs, such as you might see on a keyboard, or monitor, for example, will struggle if you attach any device that gulps current. They are fine for a mouse or other low-current consumer, but nothing more than that.

In conclusion

So use Windows' Device Manager first in the event of problems. It's a useful first base in any USB diagnostics you may have to get involved with.

 

Don Bradbury