[datenwolf]

The controller/driver side of USB-3 is still in a miserable state. USB-3 is the source of endless frustration both at the lab and at private computers. Issues range from:

USB-3 controllers won't initialize reliably if there's a single low speed device conntected, like e.g. the keyboard/mouse I've connected to the USB-3 hub my my monitor, which I'd like to connected to a USB-3 port of my computer so that I can plug thumb drives into the side ports of the monitor.

If the do initialize they take ages to go through POST.

After waking from S3 it takes several minutes(!) for all devices to come up properly. Often the OS drops the controller into USB-2 mode, because keeping it USB-3 creates interrupt storms or similar.

Just having enabled the on-board USB-3 support without anything connected may cause random POST hangs.

All of this happening on pretty recent hardware (late 2015, but still available for purchase in that configuration as of today) with latest BIOS and drivers.

And that's without the issues USB-C introduces (alternate modes, power delivery, which requires driver support, etc.).

[kakarot]

I noticed an interesting case when running Windows 7 with KVM and passing through one of my USB-3 controllers. The controller has a single port and a 3.0 hub connects to it. When I connect a USB-2 hub to the 3.0 hub, DPC latency spikes through the roof because of the interrupts. Even if there is nothing plugged into the second hub.

I wasn't sure if this was an issue with KVM, USB-3 or just a general issue with nesting hubs (even though I'm running low speed/power devices and a 3.1 port should be able to handle it) but you make it sound like it might indeed be an issue with USB-3