Private Configuration Space Port ID

The PCH incorporates a wide variety of devices and functions. The registers within these devices are mainly accessed through the primary interface, such as PCI configuration space and IO/MMIO space. Some devices also have registers that are distributed within the Private Configuration Space at individual endpoints (Target Port IDs) which are only accessible through the Sideband Interface. These Private Configuration Space Registers can be addressed via SBREG_​BAR or through SBI Index Data pair programming.