The used JGGRT 32GB PC3-14900 DDR3-1866 ECC Registered LRDIMM Server Memory is a Load-Reduced DIMM (LRDIMM). An LRDIMM is similar to a registered DIMM (RDIMM) in that it buffers electrical load on the memory controller. However, instead of plugging directly into the parallel memory bus that is connected to the memory controller's processors, the LRDIMM can navigate outside of these restrictions through the use of the Memory Buffer chips. When a server is exclusively configured with LRDIMMs, the memory controllers in the processors automatically shift to Serial Mode - all data, command, and control signals become packetized and transmitted to the Memory Buffer on the LRDIMMs. The Memory Buffer then handles all the Reads and Writes to the DRAM chips. >LRDIMMs greatly reduce the electrical loading of the DRAM chips onto the memory bus, and through a process called "Rank Multiplication," transform a Quad Rank LRDIMM into a Dual Rank memory module for the memory controller. Through the reduction of the electrical Ranks of the LRDIMM, the server is then able to support LRDIMMs at higher speeds than RDIMMs, and with fewer restrictions on sockets. This means using LRDIMMs you can configure systems with the largest possible memory footprints. If large quantities of RAM are your goal, then using a system full of LRDIMMs RAM can help you achieve twice the capacity for your PowerEdge server. 
Substitute PN: 
 708643-B21, 712384-081, 715275-001, HMT84GL7AMR4C-RD, MT72JSZS4G72LZ-1G9E
Compatible With:
 Dell PowerEdge M620 Server
 Dell PowerEdge M820 Server
 Dell PowerEdge R610 Server
 Dell PowerEdge R620 Server
 Dell PowerEdge R720 Server
 Dell PowerEdge R720XD Server
 Dell PowerEdge T620 Server
 Dell Precision Workstation R7610
 Dell Precision Workstation T7610