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I have a very strange behavior in a system where a USB3 card will work once it is pluged-in but if I later power down the PC and turn it on again it stops working. By stops working I mean that the USB devices are getting power but are not recognized.

I was playing with it trying to make it work, changing cards and trying different things. Sometimes it suddenly started working just to fail again the next test. It took me a while to reproduce and see some consistent behavior.

Here is the flow that I see. I plug the PCI-E card and boot the PC, it works. I turn the PC off with the switch on the PSU. Some leds on the motherboard remain lit for a few seconds. I wait until they die out and start the PC again. The USB3 card doesn't work now. Hard or soft resets don't matter. I need to turn off the PC and take the card out of the slot and put it back in. then the scenario happens once again.

I have tested 3 USB3 cards of two different manufacturers. all the cards have the Renesas chip though. The USB3 cards work fine in another PC. The main PC has 3 other PCI cards which work just fine. The USB3 cards are connected to a power connector (12v+5v from the PSU) as required.

Spec:
Board: Asus Z97-PRO
PSU: Seasonic 650W 80+ Gold X-650
Other PCI-e devices: Asus Radeon R9 270 DirectCU II, LSI 9211-8i, ASUS Xonar DGX 5.1

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  • I have a system with a nearly identical ASUS motherboard, and I don't have this problem, which makes me believe the problem is the PCI-E USB 3 card itself.
    – Ramhound
    Aug 17, 2016 at 10:04
  • All good USB3 cards should have an extra power input that you plugin to the PSU. Has yours got that? Aug 17, 2016 at 11:29
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    Reseating them means pulling them out, thus fully powering them down. Maybe your system does not fully shut down and keeps some power on the lines, leaving the cards in an inconsistent state. Can you try the following: Shuto down the PC. Pull the wall power plug. Try to start the PC (draining capacitor). Next morning: Plug in the wall power plug, boot and try to use the card. NB: Not as a permanent solution but as a debug tool.
    – Hennes
    Aug 17, 2016 at 11:53

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