Dell PE R720XD Owner's Manual page 41

Memory bus operating frequency can be 1600 MT/s, 1333 MT/s, 1066 MT/s, or 800 MT/s depending on:
• DIMM type (UDIMM, RDIMM, or LRDIMM)
NOTE: PowerEdge R720xd with 3.5 inch hard-drive configuration does not support LRDIMMs due to thermal
limitations.
• DIMM configuration (number of ranks)
• maximum frequency of the DIMMs
• number of DIMMs populated per channel
• DIMM operating voltage
• system profile selected (for example, Performance Optimized, Custom, or Dense Configuration Optimized)
• maximum supported DIMM frequency of the processors
The system contains 24 memory sockets split into two sets of 12 sockets, one set per processor. Each 12-socket set is
organized into four channels. In each channel, the release levers of the first socket are marked white, the second socket
black, and the third socket green.
NOTE: DIMMs in sockets A1 to A12 are assigned to processor 1 and DIMMs in sockets B1 to B12 are assigned to
processor 2.
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