Dell EMC PowerEdge R620 Owner's Manual page 40

NOTE: DIMMs in sockets A1 to A12 are assigned to processor 1 and DIMMs in sockets B1 to B12 are assigned to processor 2.
Figure 15. Memory socket locations
Memory channels are organized as follows:
Table 2. Memory channels
Processor Channel 0
Processor 1 slots A1, A5, and A9
Processor 2 slots B1, B5, and B9
The following table shows the memory populations and operating frequencies for the supported configurations.
40 Installing and removing system components
Channel 1 Channel 2
slots A2, A6, and A10 slots A3, A7, and A11
slots B2, B6, and B10 slots B3, B7, and B11
Channel 3
slots A4, A8, and A12
slots B4, B8, and B12