PCI Express Fabric Topology Configuration

The PCI Express Configuration model supports two mechanisms:

• PCI compatible configuration mechanism: The PCI compatible mechanism supports 100% binary compatibility with PCI 3.0 or later operating systems and their corresponding bus enumeration and configuration software.
• PCI Express enhanced configuration mechanism: The enhanced mechanism is provided to increase the size of available Configuration Space and to optimize access mechanisms.

Each PCI Express Link is mapped through a virtual PCI-to-PCI Bridge structure and has a logical PCI bus associated with it. The virtual PCI-to-PCI Bridge structure may be part of a PCI Express Root Complex Port, a Switch Upstream Port, or a Switch Downstream Port. A Root Port is a virtual PCI-to-PCI Bridge structure that originates a PCI Express hierarchy domain from a PCI Express Root Complex. Devices are mapped into Configuration Space such that each will respond to a particular Device Number.