Annoyances.org - Hummm..... (Windows 98 Discussion Forum)

 

Make sure that you don't have a device, or to many devices that require more power 
than your USB port can supply. A standard onboard USB port has 450 to 500mA of power 
(this is the USB standard). Examples of power used by USB devices: 

Microsoft USB mouse - 100mA
Saitek Cyborg 3D joystick - 20mA 
Kodak DC4800 camera - 2mA 
USB network card - 180mA 

A Cannon Scanner N65OU, uses 500mA of power just plugged in and up to 800mA when 
scanning 

If all of these USB devices were used at one time, they would need 1102mA of power, 
but the total provided by the motherboard USB port is only 500mA. The only way to 
use this many USB devices at once, is to get a self powered USB hub. A powered USB 
hub uses 0mA from the motherboard and has up to 5000mA available. If you want, or 
need to use many USB devices at one time, you should use a powered hub. Some devices 
like scanners, even on their own, need a powered hub. They can run off the motherboard, 
but it is not recommended if they use over 400mA. Some devices can also be plugged 
in directly and use self-power mode, rather than using the bus-power provided by 
the motherboard. You should check to see if this is an option for any devices you 
use.

To find out how much power your devices are using...open 'Device Manager'. In the 
listing 'Universal Serial Bus Controllers', select 'USB Root hub' and then the 'Power' 
tab. It will list the mA for devices plugged in. There will be a USB root hub for 
every two ports you have available on your board. This will vary between 2 and 6. 


      JmC