The Lenovo x3850 X6 and x3950 X6 servers support both DDR3 and DDR4 memory, depending on which Compute Book is used. Each X6 Compute Book holds one E7-4800 or E7-8800 processor and 24 memory DIMMs (either DDR3 or DDR4, not mixed). The x3850 X6 supports up to four Compute Books and 6 TB of memory. The x3950 X6 supports up to eight Compute Books and 12 TB of memory.

But why would you choose DDR4 memory instead of the potentially slightly lower-priced DDR3 memory?

From a physical standpoint, DDR4 is the same width as DDR3, but is slightly taller by about .9mm. The main physical difference between DDR3 and DDR4 is that DDR4 uses 288 pins compared to the 240 pins on DDR3. DDR4 DIMMs have a lower voltage requirement than DDR3 DIMMs. The lower voltage requirement results in lower power consumption. In addition, the DDR4 DIMMs make use of more efficient internal regulators.

DDR4 brings four major improvements over DDR3

  • Lower operating voltage
  • Increased power saving enhancements
  • Increased frequency
  • Improved chip density

Power consumption Study

The Lenovo performance team recently conducted a power consumption study comparing DDR3 and DDR4 memory, titled Quantifying the Power Savings by Upgrading to DDR4 Memory on Lenovo Servers. This paper clearly demonstrates that you can save on energy consumption and ultimately operational expense by simply transitioning away from DDR3 memory to DDR4 memory.

Key study findings

  • 16 GB DDR3 memory power consumption across the multiple workloads was 15-16 percent more than that of DDR4 (1) memory.
  • 32 GB DDR3 LRDIMM (2) consumes 26-30 percent more power than the DDR4 RDIMM (1).
  • You get better performance per watt efficiency with 32 GB DDR4 RDIMM at higher memory speed than 32GB DDR3 LRDIMMs (2).
  • Industry wide, 32 GB RDIMM is much more economical to purchase than 32 GB LRDIMM.

Optimizing DDR4 memory performance

But how do you make sure you are optimizing your DDR4 memory performance? The support of RDIMM and LRDIMM memory can be optimized for performance and large memory capacity requirements. Although every application has unique characteristics, adhering to best practices produces a system that is configured for optimal memory performance.

Optimizing memory performance can provide the below benefits.

  • Improve server performance
  • Reduce power consumption
  • Improve server consolidation and virtual machine performance
  • Help delay hardware refresh expenses

A Lenovo Press document titled Optimizing Memory Performance of Lenovo Servers Based on Intel Xeon E7 v3 Processors is available to help you optimize your memory performance. This paper covers memory latency, bandwidth and application performance. In addition, the paper describes performance issues that are related to CPU frequency, memory speed and population of memory DIMMs. Finally, the paper examines optimal memory configurations and best practices for the Lenovo X6 platforms.

For more information:

(1) Lenovo offers TruDDR4 DIMMs for System x servers, which are DDR4 DIMMs that are carefully tested and qualified by Lenovo to operate at speeds higher than industry standards.

(2) For DDR3, 32 GB RDIMMs are not available. You must use 32 GB LRDIMM.