Figure 189. Cable routing for onboard configuration of 4 x 2.5-inch front NVMe drive bays (using 4 x2.5-inch AnyBay 
backplane (Gen 4))
Table 30.  Mapping between backplane connectors and system board assembly connectors for onboard configuration
From To
1  NVMe 2-3 on the front backplane
1  PCIe connector 3 on the system board assembly
2  NVMe 0-1 on the front backplane
2  PCIe connector 4 on the system board assembly
252 ThinkSystem SR635 V3 User Guide