The pexusb3s42v 4 port dual bus pci express usb 30 card lets you add four dual bus usb 30 ports to your pcie x4 enabled pc dual bus architecture improves usb 30 performance by transferring data on independent channels to your computer giving you faster file transfers when multiple devices are connected traditional single bus usb 30 cards share your maximum bandwidth between all ports by employing a second host controller chipset the dual bus transmission channel is shared across two ports rather