CPC drawer I/O 1.2.5 I/O subsystem and I/O features The z14 ZR1 CPC drawer (see Figure 1-6) can include a combination of up to eight 1-port  PCIe fanouts and 2-port ICA SR PCIe coupling fanouts (numbered LG01 - LG04 and LG07 -  LG10).  The IBM z14 Model ZR1 offers a PCIe I/O infrastructure for its PCIe features that are installed  in PCIe+ I/O drawers. Up to four PCIe+ I/O drawers per z14 ZR1 are supported, which  provide space for up to 64 PCIe I/O features. Previous IBM Z server I/O infrastructures, such  as PCIe I/O drawers or I/O drawers$^{2}$, are not supported on the z14 ZR1 and cannot be carried  forward during an upgrade from a z13s. Coupling connectivity migration:  IBM z14 Model ZR1 (machine type 3907) does not  support InfiniBand coupling infrastructure. The HCA3-O fanouts for 12x IFB (FC 0171) and  HCA3-O LR fanouts for 1x IFB (FC 0170) are  not  supported. You should migrate from HCA3-O to Integrated Coupling Adapter (ICA SR) and from  HCA3-O LR to Coupling Express Long Reach (CE LR). For coupling connectivity requiring a DWDM, ensure that your DWDM equipment is  qualified to support the coupling links and timing only links. Figure 1-6 z14 ZR1 CPC drawer, front view The IBM z14 ZR1 uses PCIe fanout features for data communications between the CPC  drawer and the I/O infrastructure, and for coupling (a fully configured z14 ZR1 supports eight  PCIe fanout features). The multiple channel subsystem (CSS) architecture allows up to three  CSSs, each with 256 channels. Three  subchannel sets  are available per CSS, which allows access to many logical volumes.  The third subchannel set allows extending the amount of addressable external storage for  Parallel Access Volumes (PAVs), Peer-to-Peer Remote Copy (PPRC) secondary devices, and  IBM FlashCopyfi devices. The z14 ZR1 supports Initial Program Load (IPL) from subchannel  set 1 (SS1), or subchannel set 2 (SS2), and subchannel set 0 (SS0). For more information,  see “Initial program load from an alternative subchannel set” on page 166. The system I/O buses use the Peripheral Component IBM Interconnectfi Express (PCIe)  technology, which are also used in coupling links. 2 I/O drawers were introduced with the IBM z10™ BC and could be carried forward on earlier platform upgrades. 10  IBM 14 Model ZR1 Technical Guide