What Is Multiplexed Combined Rank DIMM (MCR DIMM) on Intel® Xeon® 6 Processors?

On Intel® Xeon® 6 Processors, MCR DIMM stands for Multiplexed Combined Rank Dual In-Line Memory Module. It's a type of memory configuration that allows for increased memory density and capacity while maintaining a relatively low number of memory channels.

Multiplexed Combined Rank DIMM (MCR DIMM), or MRDIMM, is a high-performance DDR5 memory technology for Intel Xeon 6 processors, enabling 128 bytes of data transfer per cycle instead of the standard 64 bytes. MCR DIMMs roughly double the memory bandwidth per module. 

Here's a breakdown of what each part of the term means:

1. Multiplexed: This refers to the fact that the memory signals are multiplexed, or shared, between two or more memory ranks. This allows multiple memory ranks to share the same memory channel, increasing the overall memory capacity.
2. Combined Rank: This refers to the fact that two or more memory ranks are combined to appear as a single rank to the memory controller. This allows the memory controller to address the combined rank as a single entity, simplifying the memory access and management.
3. DIMM (Dual In-Line Memory Module): This refers to the physical form factor of the memory module, which is a standard DIMM.

Key Aspects of MCR DIMM on Xeon 6:

• Performance: Delivers up to 2.3X higher performance for HPC and 2X for AI inference compared to 5th Gen Intel® Xeon® processors.
• Architecture: Utilizes a buffer on the module to combine data from two ranks, allowing 8800 MT/s+ data rates.
• Compatibility: They are compatible with DDR5 RDIMM slots and do not require software changes.
• Application: Ideal for memory-bandwidth-hungry tasks, such as AI, HPC, and high-density virtualization. 

Performance Benefits:

• MCR DIMM delivers approximately 30% greater memory bandwidth compared to RDIMM, with data transfer rates of up to 8800 MT/s for Xeon 6900P-series and 8000 MT/s for Xeon 6500P/6700P-series.
• It enables simultaneous operation of two ranks, allowing transmission of 128 bytes of data to the CPU at once, compared to 64 bytes in conventional DRAM modules.

Compatibility and Features:

• MCR DIMM maintains the same DIMM form factor for drop-in compatibility.
• It supports all reliability features of DDR5.

Target Workloads:

• Memory-bound workloads such as High-Performance Computing (HPC), Artificial Intelligence (AI), and premium cloud applications benefit significantly from MCR DIMM.

Ecosystem and Standardization:

• MCR DIMM is supported by a multi-vendor ecosystem due to Intel's collaboration with partners.
• It is available first in the industry on the Granite Rapids platform.

Bandwidth Scaling:

• MCR DIMM ensures that the growth of memory bandwidth matches the scaling of CPU core counts, maximizing system performance.

This technology is particularly suited for customers seeking the highest memory performance for demanding workloads.

For more details about MCR DIMM on Intel® Xeon® 6 Processors, visit The Intel® Xeon® 6 Processor Family or check Intel® Product Specifications