GLYPH<SM590000> PCIe+ I/O drawers are provided as required by the number of I/O adapters ordered. The  PCIe+ I/O drawers (1, 2, 3, and 4) and are installed in order in the following EIA locations:  A14B, A01B, A23B, and A31B. GLYPH<SM590000> The five possible configurations without FC 0617$^{3}$ with the view from the rear of the  system (from left to right in Figure 2-3): – The first configuration can be  a coupling facility with coupling fanouts that are installed  in the CPC Drawer only. – The second configuration includes a single PCIe+ I/O drawer that is installed at EIA  A14B and along with Configuration 1, requires only the upper pair of PDUs, which are  mounted vertically at the rear of the system in columns N and Z. – The third configuration includes the second PCIe+ I/O drawer that is installed at EIA  A01B and now requires the extra lower pair of PDUs installed to provide necessary  power. – The fourth configuration includes the third PCIe+ I/O drawer that is installed at EIA  A23B. – The fifth configuration includes the fourth PCIe+ I/O drawer that is installed at EIA  A31B (maximum I/O configuration). Figure 2-3 ZR1 Rack configurations: Rear view (without FC 0617) 2.1.2 PCIe+ I/O drawer A new PCIe+ I/O drawer is introduced with the z14 ZR1 (Machine Type 3907). The new  drawer is shown in Figure 2-4 on page 25. Each PCIe+ I/O drawer (up to four) has 16 PCIe  slots each to support the PCIe I/O infrastructure with a bandwidth of 16 GBps and includes  the following features: GLYPH<SM590000> Two I/O domains (0 and 1), each capable of hosting eight PCIe adapters, for a total of 16  I/O adapters. GLYPH<SM590000> Two PCIe switch cards provide connectivity to the PCIe fanouts that are installed in the  CPC drawer. Each I/O domain features the PCIe slots that are allocated over two PCIe  support partitions to manage the native PCIe adapters. 3 See 2.2, “16U Reserved feature (FC 0617)” on page 26. 24  IBM 14 Model ZR1 Technical Guide