The PEXUSB3S25 2-Port PCI Express USB 3.0 Card lets you add two USB 3.0 ports to your PCI Express-enabled computer system, with an optional LP4 power connector to connect to your system power supply and deliver up to 900mA of power per port to USB 3.0 bus-powered devices (500mA for USB 2.0). Enhanced with UASP support (USB Attached SCSI Protocol), this USB 3.0 controller performs up to 70% faster than conventional USB 3.0 when paired with a UASP supported enclosure (Note: UASP is not supported by all operating systems). Using a more efficient protocol than the traditional USB BOT (Bulk-Only Transport), UASP technology optimizes transfers by allowing multiple commands to be processed simultaneously, significantly increasing transfer speeds for less wait time on data transfers. See our UASP test results below for further details. The PCIe USB 3.0 adapter is compliant with USB 3.0 standards for data transfer speeds up to 5 Gbps, while still offering backward compatibility with existing USB 2.0 / 1.1 devices. For added versatility, the controller card is equipped with a standard profile bracket and includes a low-profile/half-height bracket for installation in small form-factor computers. Backed by a StarTech.com 2-year warranty and free lifetime technical support. Improved Performance with UASP UASP is supported in Windows® 8, 8.1, Server 2012 and Linux kernel 2.6.37 or later. In testing UASP performed with up to a 70% faster read / 40% faster write speed over traditional USB 3.0 at peak performance.