I've got a WD Passport hard disk with "superspeed" USB 3.0 support. When I use my USB 3.0 flash drive (this is a Lenovo X220 laptop), USB 3.0 consistently works. But when I use the passport drive, almost without fail the connection drops to USB 2.0. Touching the cable seems to immediately trigger the problem, but it seems to happen on its own though.
I've got another cable on order right now... but is it likely the cable's the issue here? Is there anything else I can check?
Well, replacing the cable seemed to make the problem go away. Oddly enough, the older cable works in my desktop but not for my laptop, and vice versa. I guess that's what I get for using bleeding edge tech.
I would check if the HDD pulls more power than is "spec" for USB 3.0 port in question. HDD publishes max power draw spec (esp. on spin-up), and USB 3.0 controller publishes the max power supplied. Do you have a way to feed power to the USB device other than over USB?
I would also check controller driver version, as it can have huge impact on stability, especially with large file transfers (beyond 100 MB). Try copying a file in question to and from USB storage, and verify consistency of its checksum. I think current Renesas driver is version 2.1.39
