NVMe cable routing
From To
BP3: NVMe 0-1, 2-3 Onboard: PCIe 1, PCIe 2
BP3: NVMe 4-5, 6-7
Onboard: PCIe 3, PCIe 4
Connections between connectors: 
1  ↔  1 ,  2  ↔  2 ,  3  ↔  3 , ...  n  ↔  n
Figure 105. NVMe cable routing (two processors)
150 ThinkSystem SR650 V2Maintenance Manual