The PEXUSB3S42V 4-Port PCI Express USB 3.0 Card lets you add four USB 3.0 ports with two dedicated 5 Gbps channels to your PCIe x4-enabled PC. This independent port architecture improves USB 3.0 performance by transferring data on two individual channels to your computer, giving you faster file transfers.When multiple devices are connected, traditional single bus USB 3.0 cards share your maximum bandwidth between all ports. By employing a second host controller chipset, the transmission channel is shared across two ports rather than four. Dedicating up to 5 Gbps for each set of two ports reduces performance bottlenecks, and effectively doubles your total available to bandwidth to 10 Gbps.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 requires a compatible operating system). 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.For high-power USB devices, this PCIe USB 3.0 card includes an optional SATA or 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). The USB 3.0 card also supports USB Battery Charging Specification 1.2 (Apple Mode only), letting you charge compatible Apple devices (iPhones and iPads) faster than a standard USB 3.0 port.The controller card is compliant with USB 3.0 standards while offering backward compatibility with existing USB 2.0 / 1.1 devices. For added versatility, the USB 3.0 PCIe 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 UASPIn testing UASP performed with up to a 70% faster read / 40% faster write speed over traditional USB 3.0 at peak performance.At the same peak in testing, UASP also showed up to an 80% reduction in required processor resources.Test results were obtained using an Intel® Ivy Bridge system, StarTech.com add-on USB 3.0 cards, a UASP-enabled StarTech.com enclosure, and a SATA III solid state drive.