A device, system and method adapted to expand a high speed data bus, such as a PCI Express (PCIe) bus, over a serial link with an expansion unit having a high speed data bus, such as a PCIe bus, without using a bridging or switching device. One primary advantage of not using a bridge or switch is that the expansion interface is completely transparent to the BIOS, processor, CPU, OS, or any other component(s) on the host motherboard be they hardware, firmware, or software. This invention does not require additional protocols such as TCP/IP, Serial ATA, Gigabit Ethernet, etc. There is also no implicit hardware or device driver latency resulting from a bridge or switch.