This 4 port USB expansion card 3 is fully functional out. The Renesas chipset at managing USB 3.0 ports, and demanded or recommended by some accessories, is supported under Windows 8.1.
Note that the card requires an additional SATA power (the same as for the hard drives or SSD), failing which it can not provide full functionality. Consequently, according to your PC, you need a splitter or extension (usually not).