The coupling links can be defined as shared between images within a CSS. They also can be  spanned across multiple CSSs in a CPC. Unlike the HCA3-O 12x InfiniBand links, the ICA SR  cannot define more than four CHPIDS per port. When STP is enabled, ICA SR coupling links  can be defined as timing-only links to other z14 ZR1, z14, and z13/z13s CPCs. The ICA SR fanout is housed in the PCIe I/O fanout slot on the z14 ZR1 CPC drawer. Up to  eight ICA SR fanouts and up to 16 ICA SR ports are supported on a z14 ZR1 CPC drawer.  This configuration enables greater connectivity for short distance coupling on a single  processor node compared to previous generations. The maximum number of ICA SR fanout  features is 16 per system for z14 ZR1 servers. The ICA SR can be used for coupling connectivity between z14/z14 ZR1 and z13/z13s  servers. It does not support connectivity to zEC12, zBC12 servers. It also cannot be  connected to HCA3-O or HCA3-O LR coupling fanouts. The ICA SR fanout requires cabling that is different from the 12x IFB cables. For distances up  to 100 meters (328 feet), OM3 fiber optic can be used. For distances up to 150 meters  (492 feet), OM4 or OM5 fiber optic cables can be used. For more information, see the  following resources: Fanout slots in the CPC drawer can be used to plug different fanouts. The CPC drawer can  hold up to eight PCIe fanout cards.  PCIe fanouts and ports are identified by an Adapter ID (AID) that is initially dependent on their  physical locations, which is unlike channels that are installed in a PCIe+ I/O drawer. Those  channels are identified by a physical channel ID (PCHID) number that is related to their  physical location. This AID must be used to assign a CHPID to the fanout in the IOCDS  definition. The CHPID assignment is done by associating the CHPID to an AID port (see  Table 4-2). GLYPH<SM590000> Planning for Fiber Optic Links , GA23-1407 GLYPH<SM590000> IBM 3907 Installation Manual for Physical Planning , GC28-6974 4.4.3 Fanout considerations Adapter ID number assignment Fanout slots Fanout Slots Features LG01 LG02 LG03 LG04 LG07 LG08 LG09 LG10 Max4 Not populated 16 17 Max12 Not p opulated 14 15 16 17 Max24 10 11 12 13 14 15 16 17 Max30 10 11 12 13 14 15 16 17 Table 4-2 AIDs and fanout locations The fanout slots are numbered LG01 - LG04 and LG07 - LG10, from left to right (LG05 and  LG06 are used for FSPs), as shown in Figure 4-2 on page 127. All fanout locations and their  AIDs for the CPC drawer are shown for reference only. Slots LG05 and LG06 never include a  fanout that is installed because they are dedicated for FSPs. Chapter 4. Central processor complex I/O system structure  127