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In a PCI Express (PCIe) system, a root complex device connects the CPU and memory subsystem to the PCI Express switch fabric composed of one or more PCIe or PCI devices. A root complex is sometimes referred to PCI root bridge.cite-ref-2[2]

The root complex generates transaction requests on behalf of the CPU, which is interconnected through a local bus. Root complex functionality may be integrated in the chipset and/or the CPU. A root complex may contain more than one PCI Express port and multiple switch devices can be connected to ports on the root complex or cascaded.cite-ref-3[3]cite-ref-4[4]

• Device Memory Map

• References

The PCIe Root Complex holds a master copy of a 'Type 1 Configuration Table' that defines the host memory space that is accessible from each Endpoint device. In addition, each PCIe Endpoint device holds a master copy of their own memory space map in the host system memory as a 'Type 0 Configuration Table', this configuration table in each device allows the host to access the local memory of a PCIe device. Both the Type 1 and Type 0 configuration tables are set up by the Host Operating System that controls the Root Complex by a process known as enumeration and which acts to build a device memory map for the system by querying each bridge, and endpoint device connected on the bus network. Similarly, a PCIe Bridge acts a tiered root complex with a "Type 0 Configuration Table".

cite-note-11. citerefrichard-solomon2015Richard Solomon (2015-06-17). "PCI Express Basics and Background" (PDF). PCI-SIG. p. 26. Retrieved 2016-04-12.

cite-note-22. ↑ "14. Protocols — PCI Bus Support — UEFI Specification 2.10 documentation". uefi.org. Retrieved 2024-11-16.

cite-note-33. ↑ "Choosing the Right Programmable Logic Solution for PCI Express Applications". Archived from the original on 21 February 2011. Retrieved 31 March 2010.

cite-note-44. ↑ "Bus Specifics (Writing Device Drivers)". docs.oracle.com. Retrieved 2020-11-14.