content_image/983092.jpg
## CPC drawer I/O 

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). 

<img src='content_image/983092.jpg'>

## 1.2.5 I/O subsystem and I/O features 

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. 

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. 

