Are USB Ports powered on always ??

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I have Compaq/HP PC's and the USB ports appears to be powered down when I go
into standby or hibernation.

I have a clone PC where the USB ports appeared to be powered on even when I
hibernate. The light on the USB keyboard stays on in hiberantion, and a
commercial device that senses the power of the USB port using it to shut down
other devices does not work on the clone, because the power is still on, but
works on the Compaq/HP, because the USB power is off.

I read somewhere it's dependent on the motherboard, so are there settings on
the motherboard to set?? When I bought the clonse PC new, I plugged and
played some USB devices and shorted out the motherboard, and the technician
at the store said I have to disconnect the device by software before
unplugging which I didn't have to do on the Compaq/HP.

Thanks.

Frank Chin
 
Some USB devices, you need to "disconnect" by the software before really
unplugging them. I do not that most USB storage device (flash disks, memory
card reader and hard drives) usually have a "write-back" (???) buffer that
needs to be "synced" up before the device is "yanked" out. USB network
adapters also need the "software" disconnect, since they need to release the
IPs and resources back to XP.

Mice, keyboards and game controls can be disconnected physically without the
"software" disconnect.
 
FrankChin said:
I have Compaq/HP PC's and the USB ports appears to be powered down when I go
into standby or hibernation.

I have a clone PC where the USB ports appeared to be powered on even when I
hibernate. The light on the USB keyboard stays on in hiberantion, and a
commercial device that senses the power of the USB port using it to shut down
other devices does not work on the clone, because the power is still on, but
works on the Compaq/HP, because the USB power is off.

I read somewhere it's dependent on the motherboard, so are there settings on
the motherboard to set?? When I bought the clonse PC new, I plugged and
played some USB devices and shorted out the motherboard, and the technician
at the store said I have to disconnect the device by software before
unplugging which I didn't have to do on the Compaq/HP.
Click to expand...

Yes, this depends on the mobo, and not all of them are created equal.
If you need some feature that is not present on your mobo, get anoter one.

--PA
 
go into Device Manager, expand the USB Controllers section, and check the
Properties for EACH of the Root Hubs that is displayed. The Power
Management tab has a check box for "Allow the computer to turn off this
device..."; if it's checked then uncheck it.

this "feature" typically only comes into play on laptops.

------

Also, SOMETIMES (but not always) the bios setting for "Legacy USB Support"
can affect this; try turning it off. Note that some USB-only keyboards
and mice might not work during the boot phase w/ this turned off, so have
a regular PS2 keyboard handy just in case (so you can "press del" to get
back in and turn it back on! Of course, check that the MOB actually has a
PS2 keyboard port, some new ones don't!).
 
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