Powered USB ports?

[Fruit2O]

Why is it that some USB peripherals will only work if plugged directly into
the PC (as opposed to being plugged into a powered USB hub)? I've had this
happen before were something didn't work - and Tech Support asked if the
device was plugged directly into the back of the PC. If it wasn't, and I
then plugged it directly in, it worked.

 

[Bob Willard]

Why is it that some USB peripherals will only work if plugged directly into
the PC (as opposed to being plugged into a powered USB hub)? I've had this
happen before were something didn't work - and Tech Support asked if the
device was plugged directly into the back of the PC. If it wasn't, and I
then plugged it directly in, it worked.

The fact that the hub is powered does not mean that the hub delivers enough
power to its clients to satisfy them.

 

[RalfG]

This applies more to USB1.1 ports, but although a powered hub may supply
enough power for your USB devices it doesn't increase the bandwidth of the
single port it is plugged into. Pointing devices and keyboards may work fine
but the available bandwidth might not be enough to support multiple
high-bandwidth devices, like Webcams, external harddrives, USB WiFi
adapters, scanners.

 

[Fruit2O]

The fact that the hub is powered does not mean that the hub delivers
enough
power to its clients to satisfy them.

I have to ask 'why not?' since there is far more power available to a
powered hub than to the receptacles at the back of the PC.

Bob (also)

 

[Fruit2O]

This applies more to USB1.1 ports, but although a powered hub may supply
enough power for your USB devices it doesn't increase the bandwidth of the
single port it is plugged into. Pointing devices and keyboards may work
fine but the available bandwidth might not be enough to support multiple
high-bandwidth devices, like Webcams, external harddrives, USB WiFi
adapters, scanners.

I have found this to be more or less opposite (using USB 2.0). For
instance, my Intuos MUST be plugged directly into the back of my PC.

 

[RalfG]

That doesn't quite contradict what I wrote. USB2 has plenty of bandwidth,
especially compared with USB 1.0/1.1. However your example is also anecdotal
so you have to be careful about interpreting it. For instance I'm running 3
USB 1.1 devices on an unpowered USB2 hub with no problems. There may be some
peculiarity in your particular hardware/setup that causes your Intuos to
need the direct connection. Looking at 2 different Intuos manuals and both
say they can be plugged into a powered USB hub.

 

[Fruit2O]

OK, understand - and thanks.

That doesn't quite contradict what I wrote. USB2 has plenty of bandwidth,
especially compared with USB 1.0/1.1. However your example is also
anecdotal so you have to be careful about interpreting it. For instance
I'm running 3 USB 1.1 devices on an unpowered USB2 hub with no problems.
There may be some peculiarity in your particular hardware/setup that
causes your Intuos to need the direct connection. Looking at 2 different
Intuos manuals and both say they can be plugged into a powered USB hub.

 

[Bob Willard]

I have to ask 'why not?' since there is far more power available to a
powered hub than to the receptacles at the back of the PC.

Bob (also)

Maybe cost considerations. Maybe marketing didn't bother to ask for much
power, so engineering didn't bother. Maybe design error. Maybe you'll
need to ask the designer of that hub, not me.