Dell PowerEdge R720 and R720xd Owner's Manual

System memory

Your system supports DDR3 unbuffered ECC DIMMs (ECC UDIMMs), registered DIMMs (RDIMMs), and load reduced DIMMs (LRDIMMs). It supports DDR3 and DDR3L voltage specifications.

  • NOTE: MT/s indicates DIMM speed in MegaTransfers per second.

Memory bus operating frequency can be 1866 MT/s, 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.
Figure 1. Memory socket locations The figure helps in locating memory sockets

Memory channels are organized as follows:

Processor 1
channel 0: slots A1, A5, and A9
channel 1: slots A2, A6, and A10
channel 2: slots A3, A7, and A11
channel 3: slots A4, A8, and A12
Processor 2
channel 0: slots B1, B5, and B9
channel 1: slots B2, B6, and B10
channel 2: slots B3, B7, and B11
channel 3: slots B4, B8, and B12

The following table shows the memory populations and operating frequencies for the supported configurations.

DIMM TypeDIMMs Populated/ChannelOperating Frequency (in MT/s)Maximum DIMM Rank/Channel
  1.5 V1.35 V 
UDIMM ECC11600, 1333, 1066, and 8001600, 1333, 1066 and 800Dual rank
21600, 1333, 1066, and 8001600, 1333, 1066 and 800Dual rank
RDIMM11866, 1600, 1333, 1066, and 8001600, 1333, 1066, and 800Dual rank
1333, 1066 and 8001066 and 800Quad rank
21866, 1600, 1333, 1066, and 8001600, 1333, 1066, and 800Dual rank
1066 and 800 1066 and 800 Quad rank
31333, 1066 and 8001066 and 800Dual rank
LRDIMM11866, 1600, 1333 and 1066 1600, 1333 and 1066 Quad rank
1600, 1333 and 1066 Not applicableOctal rank
21600, 1333 and 1066 1600, 1333 and 1066 Quad rank
1600, 1333 and 1066 Not applicable Octal rank
31333 and 1066 1066 Quad rank
 1333 and 1066 Not applicableOctal rank

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