On 1/25/2014, Paul posted:
Gene E. Bloch wrote:
On 1/25/2014, Brighty posted:
Thanks for the thoughtful reply. The Win 8 machine is a Sony Fit
i7 with two USB
3.0 ports, I've tried both, and one is a charging port so I'll
rule out a power
supply issue. The drive works faultlessly streaming video to a
Merlin jukebox
style unit which also doesn't power it.

I haven't checked this, but I have a suspicion that the extra power
on a USB3 port is only available to USB3 drives connected with a
USB3 cable...

You might try to track down a Y-cable for USB2, with a pigtail to
connect to a second USB2 output port for extra power to an external
drive.


There is a pinout here for your consideration. Only one VBUS
pin is evident. The five new USB3 signals, are a TX diff
pair, an RX diff pair, and a ground between them for crosstalk.

http://pinoutsguide.com/Slots/usb_3_...r_pinout.shtml

I can't honestly say why the USB3 current limit is higher
than the USB2 one.

Paul

Thanks. I shouldn't have been so lazy :-)

As for the larger current limit, that would just be built into the port
circuitry.

The only question, and I think it's silly even though it's my own
question, is whether the USB3 port would sense the absence of the extra
USB3 pins and thereby reduce the current limit for a USB2 device.

I didn't find an answer to that in my brief search, but in the process
I did mange to notice that USB3 is full duplex to USB2's half duplex.
That's cool.

--
Gene E. Bloch (Stumbling Bloch)