I have 2 USB ports that are behaving oddly on my ASUS P8Z77-V LK. Of the 4 USB ports on the back, 2 work fine, the other 2 will show the usb devices as being powered on during post, but as soon as Windows 7 loads, the lights go out on the USB devices and it's like the USB port is dead. It seems like they are working, at least for power all the way until Windows loads. Any ideas?
chech in your bios under usb device that ehci is enabled. on some os there has to be a usb hand off from the bios of the mb to the os on the pc. if it not turned on the usb device will turn off intill plugged back in. also check that you have the newest intel chipset driver and usb 3.0 driver.
I got into bios and enabled ehci hand off and intel xhci, still no joy. It's weird, the usb devices are getting power while it;s in bios, or even while it's booting up, but as soon as windows loads, devices plugged into two of the ports go dark.
I think because there is a limit to how much the one Intel controller can handle, so they add an additional controller that has slightly different advantages/disadvantages to provide a little variety. I believe the AsMedia ports either work better or worse for RAID configurations or something like that.