With its emergence as the new standard for high-speed portable devices, USB 3.0 performance on a modern motherboard needs to be good to ensure that data transferral bottlenecks aren't created.
We tested USB 3.0 performance using an ADATA SP300 SSD connected to an Icy Box IB-223StU3 USB 3.0 enclosure. ATTO was the benchmark used.
The Etron EJ188H USB 3.0 controller used on the 990FX Extreme9 motherboard is able to offer very good performance, but can't quite match that of the Intel Z77 chipset's ports featured on the Asus P8Z77-V motherboard, at least not until ASRock's XFast USB is activated.
Activating XFast USB's Turbo Mode allows for a healthy speed boost to be achieved by the software's USB protocol manipulations. This is a worthwhile feature that can set the ASRock 990FX Extreme9 apart from other boards without an equivalent implementation.