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The PCIe I/O drawer slots numbers are shown in Figure 4-2. 

<img src='content_image/998562.jpg'>

The I/O structure in a z14 CPC is shown in Figure 4-3 on page 152. The PCIe switch card provides the fanout from the high-speed x16 PCIe host bus to eight individual card slots. The PCIe switch card is connected to the drawers through a single x16 PCIe Gen 3 bus from a PCIe fanout card. 

In the PCIe I/O drawer, the eight I/O feature cards that directly attach to the switch card constitute an I/O domain. The PCIe I/O drawer supports concurrent add and replace I/O features to enable you to increase I/O capability as needed without having to plan ahead. 

