ASUS U3S6 PCIe x4 card SATA 6G USB 3.0 (Personal Computers)
My System: Asus P7P55D, Core i7 870, Crucial 300 128 Gb, Win 7 64 bit Prof. The card requires a PCI Express 2.0 slot. This must be at least tied with x4. It should be noted that the first PCIe 2.0 x 16 slot is usually down set to x8. This but depends