Intel celebrates the arrival of MRDIMMs — a plug and play solution for ultrafast memory that offers double the memory bandwidth of standard DRAM

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Server makers are now starting to roll out systems with these multiplexed memory modules.

Micron DDR5 MRDIMM
(Image credit: TechPowerUp)

When Intel introduced its Xeon 6 platform earlier this year, the company said that the new CPUs will support multiplexed rank dual inline memory modules (MRDIMMs) with the promise of bringing together high data transfer rates, low latency, high capacity, and predictable power consumption. Late last week, the company decided to remind the industry about its MRDIMM support, probably because server makers are beginning to roll out systems with such memory modules. For example, NEC recently announced its soon-to-be-built supercomputer that will use MRDIMMs. However, this type of memory has yet to be ratified by JEDEC. 

As server CPUs ramped up core counts in recent years, memory bandwidth available per core has decreased - despite the fact that DDR5 has greatly improved data transfer rates compared to DDR4, which created performance bottlenecks for compute-heavy workloads. MRDIMMs are designed to improve memory performance by effectively doubling available bandwidth.

MRDIMMs operate two DDR memory ranks in a multiplexed mode. These modules include not only additional memory devices but also an MRCD chip, which enables simultaneous access to both memory ranks, and MDB chips that handle multiplexing and demultiplexing. This configuration allows the CPU to communicate with MRDIMM modules at an impressive 8,800 MT/s transfer rate with Intel's Xeon 6 CPU. However, actual memory device components run at half this speed, which helps reduce latencies and power consumption. Intel's Xeon 6 processors support up to 3TB of MRDIMM memory at DDR5-8800 speed.

According to Intel and Micron, a 128GB DDR5-8800 MRDIMM provides up to 40% lower latency under load compared to a 128GB DDR5-6400 RDIMM, which greatly enhances real-world memory performance. Additionally, lowering the power consumption of memory using MRDIMMs is crucial as the energy requirements of memory modules in server systems can be on par with or even exceed the power consumption of certain server CPUs.

One of MRDIMM's main advantages is its seamless integration. It maintains the same connector and physical layout as RDIMMs, requiring no changes to the motherboard or physical configuration in servers. This compatibility means that server makers can easily integrate MRDIMMs without making any adjustments to their designs. In fact, even operators of datacenters can upgrade their Xeon 6 servers with MRDIMMs without making any adjustments to their infrastructure or software. Also, MRDIMMs retain all the reliability, availability, and serviceability features of DDR5 RDIMMs, including error correction.

Intel says it had collaborated extensively with memory vendors and industry partners to make MRDIMM an open standard. They contributed MRDIMM's specifications to the JEDEC standards organization in late 2022, and major memory vendors have already begun introducing MRDIMMs to the market, with more expected to follow..

Intel's senior engineer, George Vergis, who led the development of MRDIMMs, has also contributed to previous standards like DDR5. Vergis and his team started working on MRDIMM in 2018 and developed prototypes by 2021, achieving proof of concept before submitting MRDIMMs to be ratified by JEDEC. However, MRDIMMs remain uncertified by JEDEC, so they aren't built on a ratified standard.

Update 11/20/2024 10:40 am: Clarified JEDEC status for MRDIMMs.

Anton Shilov
Anton Shilov
Contributing Writer

Anton Shilov is a contributing writer at Tom’s Hardware. Over the past couple of decades, he has covered everything from CPUs and GPUs to supercomputers and from modern process technologies and latest fab tools to high-tech industry trends.

32 Comments Comment from the forums
  • bit_user
    These "MRDIMMs" are actually MCR-DIMMs, which is a proprietary scheme Intel worked up with SK Hynix, as reported here:
    https://www.tomshardware.com/news/sk-hynix-develops-mcr-dimm
    Meanwhile, AMD has been working with JEDEC to develop a standard MRDIMM spec, which is why they don't yet have a competing solution on the market.
    https://www.tomshardware.com/news/amd-advocates-ddr5-mrdimms-with-speeds-up-to-17600-mts
    Intel's rebranding of MCR-DIMMs is just creating market confusion. Saying it offered their MCR-DIMM tech to JEDEC is just further trying to muddy the waters.

    I predict Intel will switch to JEDEC MRDIMMs, once they're finalized. I wouldn't count on the current generation of rebranded MCR-DIMMs being supported in future products. This view is underscored by this (paywalled) op ed:
    https://axautikgroupllc.substack.com/p/new-mcr-dimm-modules-are-doomed
    Reply
  • EzzyB
    bit_user said:
    These "MRDIMMs" are actually MCR-DIMMs, which is a proprietary scheme Intel worked up with SK Hynix, as reported here:
    https://www.tomshardware.com/news/sk-hynix-develops-mcr-dimm
    Meanwhile, AMD has been working with JEDEC to develop a standard MRDIMM spec, which is why they don't yet have a competing solution on the market.
    https://www.tomshardware.com/news/amd-advocates-ddr5-mrdimms-with-speeds-up-to-17600-mts
    Intel's rebranding of MCR-DIMMs is just creating market confusion. Saying it offered their MCR-DIMM tech to JEDEC is just further trying to muddy the waters.

    I predict Intel will switch to JEDEC MRDIMMs, once they're finalized. I wouldn't count on the current generation of rebranded MCR-DIMMs being supported in future products. This view is underscored by this (paywalled) op ed:
    https://axautikgroupllc.substack.com/p/new-mcr-dimm-modules-are-doomed
    The horse is out of the barn. There is a power in being first to market, especially if Intel has memory makers already producing the modules and calling them MRDIMM.

    Remember, this isn't done, it's just the first iteration, spec 1. There are certainly plans to increase the bandwidth further, and this seems to fulfill the performance of the first tier. So this will continue to be spec 1.

    I'm not sure what is holding back current AMD processors or chipsets from using these modules, but convincing SK Hynix and Micron to make an AMD-only version of what the largest memory producers are already calling MRDIMM might be a tough task. AMD would probably be better off turning their efforts to be first to market to support spec 2.

    This kind of thing isn't new. It's quite common, Intel made a chip that can benefit from a new kind of memory. It convinced manufacturers to make it. Waiting on a standards committee to wave a magic wand negates their technological advantage. (See also Microsoft waiting on OpenGL to get off their ass and simply releasing DirectX instead.) Expect the memory manufacturers to dig in here, because they've already tooled up.
    Reply
  • bit_user
    EzzyB said:
    I'm not sure what is holding back current AMD processors or chipsets from using these modules, but convincing SK Hynix and Micron to make an AMD-only version
    AMD is working to support the official JEDEC standard, not something AMD-specific. Once that's out, it's what memory makers will naturally prefer to manufacture. The computing world consists of more than just Intel and AMD. In the server memory market, there's the growing ranks of ARM and upcoming RISC-V CPUs, which will also prefer to implement a JEDEC standard.

    Nvidia has a history of taking Intel's approach and jointly developing custom memory specs, like GDDR6X. The downside is that it ties them to sourcing only from a single manufacturer, rather than being able to harness open market competition to achieve better pricing and availability.
    Reply
  • Eximo
    That's DRDIMM to you. He didn't spend all those years at memory school to be called MR.
    Reply
  • EzzyB
    bit_user said:
    AMD is working to support the official JEDEC standard, not something AMD-specific. Once that's out, it's what memory makers will naturally prefer to manufacture. The computing world consists of more than just Intel and AMD. In the server memory market, there's the growing ranks of ARM and upcoming RISC-V CPUs, which will also prefer to implement a JEDEC standard.

    Nvidia has a history of taking Intel's approach and jointly developing custom memory specs, like GDDR6X. The downside is that it ties them to sourcing only from a single manufacturer, rather than being able to harness open market competition to achieve better pricing and availability.
    What I'm saying is that real standards are what become standards. It's like a discussion I had 15 years ago when some open source evangelist was ranting that the document he was trying to upload wasn't supported. My GOD! He used Libre Office to create that file and 20 nerds had gathered at the conference room at the Peoria Holiday Inn and declared it a standard damnit. He'd burn in hell before he used .doc. But, at that time, what was the real standard?

    Even though Microsoft was, by far, the largest financial backer of OpenGL that standard committee was terrified that anything it did might actually benefit Microsoft. The result was that DirectX 9 was released before OpenGL 2.0 and OpenGL was simply pushed to the back burner. Imagine if the only games you could play in the last 25 years had to be OpenGL compliant. So how can it be a "standard"?

    One certainly can't blame Intel here. They have a capability, they offered the spec to JEDEC two years ago and, what? Where is JEDEC here? We don't know. We don't know if AMD has a better standard. We don't know if it has manufacturing challenges even it it is a better standard. But, by doing nothing they run the risk of no longer controlling the standard at all because it's out in the wild.

    Standards like GDDR6 are still standards even if some governing body didn't approve them simply because they are the most used. This idea that some group of 20 Nerds at the Peoria Holiday Inn has to bless them might look good on paper, but it doesn't necessarily make them standard.
    Reply
  • Sluggotg
    So I guess we call them Mister DIMMS? I always called EDO RAM, "EE-DOE RAM", (But I think I was alone on that).
    Reply
  • 80251
    So is this memory tech poised to replace CUDIMMs? Are CUDIMMs and MRDIMMs compatible w/standard DDR5 tech or is a new IMC and slot std. required? Will MRDIMM be coming to the consumer market?
    Reply
  • thestryker
    bit_user said:
    Intel's rebranding of MCR-DIMMs is just creating market confusion.
    This is the part I don't really understand at all because I fail to see the benefit to Intel. They donated the MCR design to JEDEC in what I imagine is a fashion similar to Dell and CAMM which makes sense. Rebranding MCR to MR doesn't really make sense though unless it's going to be compatible. I don't see how it would benefit Intel in any way because it would also confuse their own customers.
    Reply
  • thestryker
    80251 said:
    So is this memory tech poised to replace CUDIMMs? Are CUDIMMs and MRDIMMs compatible w/standard DDR5 tech or is a new IMC and slot std. required? Will MRDIMM be coming to the consumer market?
    It's unlikely this will come to the consumer market, does require an IMC that knows what to do with it like CUDIMMs do, and it is slot compatible with DDR5.
    Reply
  • 4m12020
    bit_user said:
    These "MRDIMMs" are actually MCR-DIMMs, which is a proprietary scheme Intel worked up with SK Hynix, as reported here:
    https://www.tomshardware.com/news/sk-hynix-develops-mcr-dimm
    Meanwhile, AMD has been working with JEDEC to develop a standard MRDIMM spec, which is why they don't yet have a competing solution on the market.
    https://www.tomshardware.com/news/amd-advocates-ddr5-mrdimms-with-speeds-up-to-17600-mts
    Intel's rebranding of MCR-DIMMs is just creating market confusion. Saying it offered their MCR-DIMM tech to JEDEC is just further trying to muddy the waters.

    I predict Intel will switch to JEDEC MRDIMMs, once they're finalized. I wouldn't count on the current generation of rebranded MCR-DIMMs being supported in future products. This view is underscored by this (paywalled) op ed:
    https://axautikgroupllc.substack.com/p/new-mcr-dimm-modules-are-doomed

    MRDIMM and MCRDIMM are both types of high-performance DDR5 memory modules designed to improve the efficiency and bandwidth of server systems. While they share similarities, they have distinct characteristics and are backed by different industry alliances.
    MCRDIMM (Multiplexer Combined Ranks DIMM):
    * Backed by: Intel and SK Hynix
    * Key feature: Uses a multiplexer buffer to access both ranks of the DIMM simultaneously, doubling the data transfer rate to the CPU.
    * Target speed: 8800 MT/s (first generation), with potential for higher speeds in future generations.
    * Compatibility: Designed to work with Intel's 6th Generation Xeon Scalable "Granite Rapids" platforms.
    MRDIMM (Multi-Ranked Buffered DIMM):
    * Backed by: JEDEC, AMD, Google, Microsoft, and Intel
    * Key feature: Similar to MCRDIMM, it uses a multiplexer buffer to access both ranks simultaneously, increasing bandwidth.
    * Target speed: 8800 MT/s (first generation), with plans to reach 12,800 MT/s and 17,600 MT/s in subsequent generations.
    * Compatibility: More widely supported by various vendors and platforms.
    In summary:
    Both MCRDIMM and MRDIMM aim to enhance server performance by doubling the data transfer rate from the DIMM to the CPU. MCRDIMM is currently more specific to Intel's platform, while MRDIMM is more broadly supported by the industry. As technology advances, both types of DIMMs are expected to offer even higher speeds and capacities, driving the performance of future server systems.

    bit_user said:

    Reply