Micron showed unusual 256 GB MCRDIMM RAM modules at the Nvidia GTC 2024 conference. These high-height modules are designed for the new generation of server systems, including those based on the future Intel Xeon Scalable Granite Rapids processors. Micron said it has already begun sending samples to interested buyers.
The 256 GB MCRDIMM DDR5 memory modules demonstrated by the manufacturer operate at a speed of 8800 MHz. They are designed for 1U server systems. These memory modules are based on 32-gigabit DDR5 chips. On each side of such a module there are 40 memory chips. The power consumption of one 256 GB MCRDIMM DDR5-8800 RAM module is about 20 W, which is relatively little, considering that the 128 GB DDR5-8000 RDIMM modules previously released by the same manufacturer with the standard DDR5-4800 profile consume 10 W.
Multiplexer Combined Ranks (MCR) DIMMs are a type of dual-rank RAM modules that operate two ranks in parallel by using a special buffer. This buffer allows the two physical ranks to act as if they were two separate memory modules running in parallel. This effectively doubles the performance of such modules by simultaneously fetching 128 bytes of data from both ranks per clock cycle. The buffer works with its host DDR5 memory controller, which allows the memory to operate at speeds higher than the standard. In this case we are talking about 8800 MT/s.
Typically, modules with two physical ranks function as one module. Thus, the CPU or memory controller retrieves only 64 bytes of data per clock cycle. MCRDIMM memory doubles this value, thereby significantly increasing the capacity and performance of each module.
The fact that Micron decided to show its 256 GB MCRDIMM memory modules at the Nvidia GTC 2024 AI conference may indicate that the company is considering this product as a solution for next-generation AI servers, for example, based on Intel processors Xeon Scalable Granite Rapids. Systems based on them will use huge amounts of memory to train AI models, so these RAM modules will come in handy. The Intel Xeon Scalable Granite Rapids chips themselves will support 12-channel memory mode with two modules per channel. Thus, based on Micron modules, it will be possible to create servers with 3 TB of RAM when using 12 memory slots and up to 6 TB of RAM when using 24 memory slots.
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