2.7.1 Redundant I/O interconnect A fanout can be repaired concurrently with the use of redundant I/O interconnect. For more  information, see 2.7.1, “Redundant I/O interconnect” on page 70.  The following types of fanouts are available: When configured for availability, the channels and coupling links are balanced across CPC  drawers. In a system that is configured for maximum availability, alternative paths maintain  access to critical I/O devices, such as disks and networks. The CHPID Mapping Tool can be  used to assist with configuring a system for high availability. Enhanced (CPC) drawer availability (EDA) allows a single CPC drawer in a multidrawer CPC  to be removed and reinstalled (serviced) concurrently for an upgrade or a repair. Removing a  CPC drawer means that the connectivity to the I/O devices that are connected to that CPC  drawer is lost. To prevent connectivity loss, the redundant I/O interconnect feature allows you  to maintain connection to critical I/O devices (except for ICA SR1.1) when a CPC drawer is  removed. Redundancy is provided for PCIe I/O interconnects. The PCIe+ I/O drawer supports up to 16 PCIe features, which are organized in two hardware  domains (for each drawer). The infrastructure for the fanout to I/O drawers and external  coupling is shown in Figure 2-26. The new PCIe+ Gen3 fanout cards are used to provide the connection from the PU SCM  PCIe Bridge Unit (PBU), which uses split the PCIe Gen4 (@32GBps) processor busses into  two PCIe Gen3 x16 (@16 GBps) interfaces to the PCIe switch card in the PCIe+ I/O drawer.  70  IBM z15 (8561) Technical Guide Figure 2-26 Infrastructure for PCIe+ I/O drawer (system with two PCIe+ I/O drawers) GLYPH<SM590000> A new PCIe+ Generation3 dual port fanout card: This fanout provides connectivity to the  PCIe switch cards in the PCIe+ I/O drawer. GLYPH<SM590000> A new Integrated Coupling Adapter (ICA SR1.1): This adapter provides coupling  connectivity to z15, z14, and z13 servers.