What is the difference between DDR5 RDIMM and MRDIMM for servers?
MRDIMM gives Intel Xeon 6 servers a higher memory data rate at one DIMM per channel. RDIMM works across server platforms and fills two DIMMs per channel for capacity.
MRDIMM, the multiplexed rank DIMM, raises the memory data rate on Intel Xeon 6 servers. Micron rates its MRDIMMs at up to 8,800 MT/s. Intel lists DDR5-6400 for RDIMM on the same processors. RDIMM remains the general-purpose server module. It fills two DIMMs per channel when capacity matters more than bandwidth.
How MRDIMM works
Micron describes MRDIMM as an evolution of DDR5 DIMM technology, with a multiplexer buffer on the module that manages data across multiple memory ranks. In tests Micron cites, its 128 GB MRDIMM at 8,800 MT/s showed up to 40% lower latency than a 128 GB RDIMM at 6,400 MT/s. Micron also says its second-generation design is under definition at JEDEC.
Speed on real platforms
Intel lists MRDIMM at up to 8,800 MT/s on Xeon 6 processors with P-cores. Each server platform sets its own figures. On the Lenovo ThinkSystem SR650 V4, a Xeon 6700P and 6500P server, Lenovo supports MRDIMMs at up to 8000 MHz and RDIMMs at up to 6400 MHz, both at one DIMM per channel.
DIMMs per channel and capacity
The SR650 V4 shows the trade. Lenovo supports MRDIMMs there at one DIMM per channel, with no support for two. RDIMMs run at two DIMMs per channel at up to 5200 MHz. Lenovo lists its 64GB MRDIMM at eight per processor and its 64GB RDIMM at up to sixteen per processor. With 256GB 3DS RDIMMs in all 32 slots, the server reaches 8TB.
Micron offers MRDIMMs from 32 GB up to 256 GB. Samsung lists both DDR5 RDIMM and MRDIMM at up to 256 GB per module.
Platform support
Micron states that its MRDIMMs are compatible with Intel Xeon 6 processors and no other platform. A fleet that mixes server platforms standardizes on RDIMM. Within one server, Lenovo requires all installed RDIMMs to be identical part numbers.
Which one to choose
Choose MRDIMM for memory-bandwidth-bound workloads on Xeon 6 servers populated at one DIMM per channel. Choose RDIMM for maximum capacity per server, for two DIMMs per channel and for fleets that span more than one platform.
How to buy it through Gatewell USA
Both are quoted by the tray on the quote form. Name the maker part number, or the capacity, speed and server model, with the count. A quote comes back within one business day.