PCIe I/O paths are routed from CMP root complexes, through PCIe switches, to a destination PCIe slot and/or EMS card. Each CMP provides two root complexes, allowing it to attach to two PCIe switches. Each PCIe switch connects to two root complexes. In an ideal configuration, with all components present and functioning, two CMPs connect to each PCIe switch, and that switch is partitioned into two virtual switches with independent traffic channels. This configuration maximizes I/O bandwidth.
In the event of a failure or missing CMPs (and associated root complexes), the PCIe switch is merged into a single switch so that the remaining root complex services all downstream ports. This configuration maximizes I/O connectivity.
As long as there are no changes in the hardware components present in the configuration, the I/O paths will remain consistent following a boot or reset. If there are changes in the number of CMPs present (for example, if CMPs are added or removed), some I/O paths might change.