A means for extending a PCI System of a host computer via software-centric virtualization. A Root Complex is virtualized at the host computer, and physically separated with a portion located remotely at an Endpoint, such as at a Remote Bus Adapter. One aspect of the invention avoids the need for a Host Bus Adapter. The invention utilizes 1 Gbps-10 Gbps or greater connectivity via the host's existing standard LAN adapter along with unique software to form the virtualization solution. The invention works within a host's PCI Express topology, extending the topology by adding an entire virtual I/O hierarchy via virtualization. The invention enables I/O virtualization in those implementations where a specialized host bus may not be desirable or feasible. Some examples of this may be a laptop computer, an embedded design, a cost-sensitive design, or a blade host where expansion slots are not available or accessible.