DDR5 Memory Bandwidth for Dell PowerEdge R7725 Servers with 5th Gen AMD EPYC Processors

Summary

Dell PowerEdge R7725 servers, powered by the latest 5th Gen AMD EPYC processors, are at the forefront of new server technology. These 17th Gen Dell PowerEdge rack servers are available in single and dual socket 2U form factors for mass market use.

In dual-socket systems like the R7725, each socket provides 12 DIMM channels at speeds up to 6400 MT/s. Single-socket implementations of 5th Gen EPYC provide 12 memory channels with two DIMMs per channel, allowing for 24 DIMMs. The single-socket R7715 provides speeds of 5200 MT/s when one DIMM is installed per channel and 4400 MT/s when 2 DIMMs are installed per channel.

This paper compares memory bandwidth performance measured on these new servers with various memory configurations to previous generation servers powered by 4th Gen AMD EPYC processors.

AMD EPYC 5th Gen Memory Architecture

5th Gen AMD EPYC processors are built on AMD DDR5 memory support, which was first introduced in the previous generation memory controller. With a chiplet design with a central I/O chiplet surrounded by compute chiplets, the memory operates at speeds up to 6400 MT/s, a more than 30% increase over the 4800 MT/s supported by previous 4th Gen AMD EPYC processors.

Despite the speed improvements, the Dell PowerEdge R7725 and R7715 processors for the 5th Gen AMD EPYC mainstream models retain the same memory topologies as the 4th Gen AMD PowerEdge offerings.

Memory bandwidth test

The STREAM memory test is a synthetic benchmark designed to measure sustained memory throughput, which is the speed at which data can move to and from memory under real-world conditions. It is widely used in high-performance computing (HPC), artificial intelligence, and machine learning environments, where memory bandwidth is often the limiting factor. The STREAM test assesses how efficiently a system can handle large data transfers, which is critical for workloads that process large data sets.

First, we look at memory performance on the PowerEdge R7725. This data covers different memory channel groups with 64GB DIMMs running at a maximum frequency of 6400 MT/s.

The data presented here was collected with both factory default BIOS configurations and customized BIOS settings. The following systems were tested:

• Previous generation Dell PowerEdge R7625, powered by 4th Gen AMD EPYC processors, features up to 12 DDR5 DIMMs with 4800M transactions/s per channel
• The latest generation Dell PowerEdge R7725, powered by 5th Gen AMD EPYC processors, features up to 12 DDR5 6400 MT/s DIMMs per socket

Figure 1. Trends in aggregate system memory bandwidth by DIMM count for 5th Gen AMD EPYC-based PowerEdge servers with default BIOS settings

Figure 2. Trends in aggregate system memory bandwidth by DIMM count for 5th Gen AMD EPYC-based PowerEdge servers with BIOS settings configured

Figure 3. Trends in aggregate system memory bandwidth by DIMM count for PowerEdge servers based on 4th Gen AMD EPYC processors with BIOS settings configured

On 2-socket platforms, these results represent a 12.6% performance increase over the previous generation in a fully populated or balanced memory configuration. Near-balanced configurations represent an average of nearly 19% performance increase over EPYC 4th ^generation This level of performance contributes to the system performance that customers have come to expect from a Dell PowerEdge server solution.

Next, we look at the same data for the single-processor Dell PowerEdge R7715. Note that configurations with 15, 14, and 13 DIMM slots are not supported, so data for these configurations is not presented.

Figure 4. Trends in aggregate system memory bandwidth by DIMM count for 5th Gen AMD EPYC-based PowerEdge servers with default BIOS settings

Figure 5. Trends in aggregate system memory bandwidth by DIMM count for 5th Gen AMD EPYC-based PowerEdge servers with BIOS settings configured

In a single-socket configuration, the BIOS setting provides a performance increase of over 100% in unbalanced configurations, establishing near performance parity in this memory bandwidth workload compared to balanced configurations.

The following BIOS configuration was used to achieve these optimized BIOS results:

Key findings

This data reflects the continued advancement of DDR5 memory technology and Dell Technologies’ expertise in platforms powered by world-class AMD processors. Regardless of the memory configuration you choose for your Dell 5th Gen AMD rack solution, you won’t be disappointed with the performance.

Server configurations

Testing was conducted by Dell Technologies on a PowerEdge R7725 with AMD 5- ^th generation 9555 and Dell PowerEdge R7715 with AMD 5 ^-th generation 9655P.