Backplane
Use the section to understand the cable routing for backplanes.
This topic contains the following information: 
•  “Server models with eight 2.5-inch drives” on page 33
•  “Server models with sixteen 2.5-inch drives” on page 38
•  “Server models with twenty-four 2.5-inch drives” on page 53
•  “Server models with eight 3.5-inch drives” on page 78
•  “Server models with twelve 3.5-inch drives” on page 81
Before you route cables for backplanes, observe the adapter priority and the PCIe slot selection priority when 
installing the NVMe switch adapter or a RAID adapter.
•  Adapter priority: NVMe switch adapter, 24i RAID adapter, 8i RAID adapter, 16i RAID adapter
•  PCIe slot selection priority when installing the NVMe switch adapter:
Number of installed processors
PCIe slot selection priority
One processor
1
Two processors 1, 5, 6
•  PCIe slot selection priority when installing a 24i RAID adapter:
Number of installed processors
PCIe slot selection priority
One processor
1, 2, 3
Two processors 1, 2, 3, 5, 6
•  PCIe slot selection priority when installing a 8i or 16i RAID adapter:
Number of installed processors PCIe slot selection priority
One processor
7, 4, 2, 3, 1
Two processors 7, 4, 2, 3, 1, 5, 6
Notes: 
•  The PCIe slot 7 refers to the RAID adapter slot on the system board.
•  If the rear hot-swap drive assembly is installed, PCIe slots 1, 2, and 3 will become unavailable because the 
space is occupied by the rear hot-swap drive assembly.
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ThinkSystem SR650 Maintenance Manual