That's not really relevant as long as you can't choose the directions for the channels. You are only going to get one channel in each direction.
Edit: Whoa. I just re-read parts of the Intel documentation, and it seems there are indeed two independent downstream channels. My bad. It also looks like there is no provision for using both channels for a single device? I have no idea.
Edit: Whoa. I just re-read parts of the Intel documentation, and it seems there are indeed two independent downstream channels. My bad. It also looks like there is no provision for using both channels for a single device? I have no idea.