MCR DIMM – Multiplexer Combined Ranks DIMM (Dual Inline Memory Module). DIMMs are cards holding DRAM which fit in sockets on CPU motherboards. As CPUs get more and more cores the number of sockets does not increase so fast causing  memory bandwidth to be insufficient to keep all the cores busy. Gen 3 Xeon CPUs (IceLake) support 8 sockets. An MCR DIMM has two ranks with buffer on each module meaning the MCR DIMM can transfer 128 bytes per cycle (64 bytes from each rank) which has roughly twice as much as a normal, single rank DIMM.

SK hynix introduced its MCR DIMM product in 2022. It operate at the data rate of minimum 8Gbps, and at least 80 percent faster than 4.8Gbps of the existing DDR5 products.