Lenovo ThinkSystem SR635 V3 User Manual page 262

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
NVMe 2-3 on the front backplane
1
NVMe 0-1 on the front backplane
2
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To
PCIe connector 3 on the system board assembly
1
PCIe connector 4 on the system board assembly
2