Very strange usb problem??

[Jhill]

I couldn't get my computer to reconize my digital camera or my webcam through the usb ports. I made sure usb was turned on in the bios. I plug them in and restart xp pro and nothing happened.

Then I hooked up my powered usb hub and hooked my camera up through that and it works! Why will it work through the hub but not work when I hook it straight into the usb port? The hub is plugged into the same port I tried before.

Any suggestions?

 

[Peter]

That an USB powered device? If yes, then it simply draws more power than the USB specification allows. Mainboards typically flip their overload cutoff switch much earlier than hubs do.

Devices that draw up to 1000 mA have become quite common now in the "cheap" area. However USB allows only 500 mA per port. Great. Save a power supply to make your device look a better bargain, then make customer buy a hub.

regards, Peter

 

[Jhill]

The wierd thihng is that I have an Enlight 340 watt power supply. A slso have an ECS K7S5A. Do you think it could be the motherboard doing this?
I also tried a usb webcam and a usb game controller and neither of them work straight into the port but they do work in the hub.

 

[Peter]

That's not a PSU thing - the USB specification limits per-port power to 500 mA, and any USB hub (including the root hubs on the mainboard) is supposed to cut the port's power off if this is exceeded to avoid zapped traces or other components. External hubs use to have a much higher cutoff threshold.

regards, Peter