The 4JMGM 64GB LRDIMM is a Quad Rank X4 DDR4 Memory module that operates at speeds up to 2666MHz and has a CL19 latency. It is a Load-Reduced Memory and is ECC Registered. It conforms to the industry standard DIMM layout of 288 pins and is compatible with systems that take DDR4 LRDIMM memory.

 The 4JMGM 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 controllers 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 server System.

Substitute PN:
 840759-091
 A9781930
 M386A8K40BM2-CTD7Q

Compatible With:
 Dell PowerEdge C4130, C4140, FC430, FC630, FC830, M630, M830, T440, T630, T640
 Dell EMC PowerEdge C6420, FC640, M640, MX740c, MX840c, R440, R540, R630, R640, R6415, R730, R730xd, R740, R740xd, R740xd2, R7415, R7425, R830, R840, R930, R940, R940XA, T440, T640, XR2