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I'm shopping for a new laptop and many specs list USB ports as "1 powered USB, 2 USB 2.0". What's the difference? Aren't regular USB ports powered, as in capable of powering an external device?

Update things are getting confused. I have a netbook which lists a "powered" USB port, and being a netbook it could well be that it's the only port capable of powering an external hard disk. But then I have another laptop that lists a powered USB port too, and it's color coded, and the software on the laptopo speaks of an "always on" port that could be used to power a device even when the laptop is off. So it could well be that "powered USB port" could refer to both types.

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2 Answers 2

up vote 8 down vote accepted

Look at this: http://en.wikipedia.org/wiki/USB#Power

The "non-powered" USB ports most likely support only "low power" USB devices, ie. ones using less than 100mA of power, like mice or keyboard.

Powered ports are needed for external (2.5", bigger need power supply) hard drives and charging cell phones.

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You are missing an important fact: Usually those specially colored ports provide power even if the notebook is not running. –  Robert Oct 12 '11 at 9:50
    
It's completely a matter of BIOS and motherboard settings if they deliver power when computer is not running. On desktop motherboards it's sometimes configurable with jumpers. However, this has nothing to do with USB standard; it's just that motherboard chooses to keep some USB ports active on sleep, while shutting down the rest. –  Zds Oct 12 '11 at 10:09

Generally they provide some power but not much. If you want to power some hard drives or other devices, or an unpowered hub, you need a powered port.

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