Add-in Cards Help Meet Expanding Server Memory Needs

As high-density data center applications become more commonplace, design engineers have to grapple with adding memory capacity in a cost and space-effective manner. SMART Modular Technologies, a division of SGH  has introduced a family of Add-In Cards (AICs) which implements the Compute Express Link (CXL^®) standard and also supports industry standard DDR5 DIMMs. According to the company, these are the first in their class, high-density DIMM AICs to adopt the CXL protocol.

The SMART 4-DIMM and 8-DIMM products enable server and data center architects to add up to 4TB of memory in a familiar, easy-to-deploy form factor.  Built with advanced CXL controllers, the add-in cards eliminate memory bandwidth bottlenecks and capacity constraints for compute-intensive workloads encountered in artificial intelligence (AI), high-performance computing (HPC), and machine learning (ML). Attempts to add more memory via the traditional DIMM-based parallel bus interface are becoming problematic due to pin limitations on CPUs, so the industry is turning to CXL-based solutions which are more pin-efficient.

CXL also enables lower-cost scaling of memory capacity. Tom Quinn, Senior Vice President of Business Development, said in an interview with Design News that the add-in card is a more cost-effective means of adding memory than just using DIMM modules. According to Quinn, using an 8-DIMM CXL AIC with 64-GB DDR5 DIMMs would cost 33% less per terabyte than using eight 64 GB DDR5 DIMMs.  Replacing high density RDIMMs with a greater number of lower density modules can lower system memory costs.  

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The add-in cards are available in type 3 PCIe Gen5 full height, half-length (FHHL) PCIe form factor. The 4-DIMM AIC (CXA-4F1W) accommodates four DDR5 RDIMMs with a maximum of 2TB of memory capacity when using 512GB RDIMMs, and the 8-DIMM AIC (CXA-8F2W) accommodates eight DDR5 RDIMMs with a maximum of 4TB of memory capacity.  

The 4-DIMM AIC uses a single CXL controller that implements one x16 CXL port, while the 8-DIMM AIC uses two CXL controllers to implement two x8 ports, both resulting in a total bandwidth of 64GB/s. Both AICs offer enhanced security features with in-band or side-band (SMBus) monitoring capability. In order to accelerate memory processing, these add-in cards are compatible with SMART’s Zefr^™ ZDIMMs^™.