Micron Samples 256 GB DDR5-8800 MCR DIMMs: Massive Modules for Massive Servers

Micron Samples 256 GB DDR5-8800 MCR DIMMs: Massive Modules for Massive Servers

Micron announced this week that it has begun sampling its 256 GB multiplexer combined (MCR) DIMMs, the company's highest-capacity memory modules to date. These brand new DDR5-based MCRDIMMs are aimed at next-generation servers, specifically those powered by Intel's Xeon Scalable 'Granite Rapids' processors that are set to support 12 or 24 memory slots per socket. The use of these modules can enable data center machines with 3 TB or 6 TB of memory, with shared arrays allowing effective data rates of DDR5-8800.

“We also began sampling our 256 GB MCRDIMM module, which further increases performance and increases DRAM content per server,” said Micron Chief Executive Sanjay Mehrotra said in prepared remarks for the company's earnings call this week.

In addition to announcing sampling of these modules, Micron also demonstrated them at NVIDIA's GTC conference, where server vendors and consumers alike are busy building new servers for the next generation of AI accelerators. From our colleagues Tom's Hardware Managed to get some images of Micron's 256 GB DDR5-8800 MCR DIMMs.

Image credit: Tom's Hardware

Apparently, Micron's 256 GB DDR5-8800 MCRDIMMs come in two varieties: a tall module with 80 DRAM chips distributed on both sides, and a standard-height module using 2Hi stacked packages. Both are based on monolithic 32 Gb DDR5 ICs and are engineered to meet a variety of server configurations including 1U servers with standard height MCRDIMMs. The tall version uses about 20W of power, which is in line with expectations. 128 GB DDR5-8000 RDIMM Consumes about 10W in DDR5-4800 mode. I have no idea about the power consumption of the version that uses the 2Hi packages, though expect it to be a bit hot and difficult to cool.

Image credit: Tom's Hardware

Multiplexer Combined Rank (MCR) DIMMs are dual-rank memory modules that contain a special buffer that allows both ranks to operate simultaneously. This buffer enables both physical ranks to operate as if they were separate modules operating in parallel, allowing simultaneous retrieval of 128 bytes of data per clock cycle from both ranks (when regular memory modules compared to 64 bytes per cycle), effectively doubling the performance of a single module. Of course, since the modules retain the physical interface of standard DDR5 modules (ie 72 bits), the buffer works with the host at a much higher data transfer rate to transfer the received data to the host CPU. This speed exceeds standard DDR5 specifications, reaching 8800 MT/s in this case.

While MCR DIMMs make memory modules slightly more complex than regular RDIMMs, they increase memory subsystem performance and capacity without increasing the number of memory modules involved, making server motherboards easier to build. These modules are poised to play a major role in enabling the next generation of servers to handle increasingly demanding applications, especially in the AI ​​field.

Sources: Tom's Hardware, Micron

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