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