The processors in the AMD EPYC 7002 Rome and AMD EPYC 7003 Milan series have more than eight memory controllers that can be connected to a memory channel. Up to two DIMMs are possible per channel. To achieve the best possible overall performance, it is helpful to ensure a balanced allocation. This article presents frequently used DIMM configurations.

The following properties characterise processors of the AMD EPYC 7002/7003 series in terms of memory:

• 8 memory controllers per CPU
• 1 memory channel per memory controller
• 2 DIMMs per channel, with a maximum of 16 DIMMs per CPU and 32 DIMMs in a dual-CPU system

The highest possible memory bandwidth is particularly relevant in the HPC environment. In other application areas, memory bandwidth has a lower influence on overall performance and depends on the specific application. For example, tests show that performance of up to 90% can be achieved with a memory bandwidth of just 35%. RAM assemblies with fewer modules reduce the maximum bandwidth. However, they consume less energy and offer good expansion potential for the future.

The following chart illustrates the correct configuration of the RAM slots.

The following table shows possible DIMM-configurations of a Single-CPU system with a mainboard with 16 DIMM slots (for example ASUS KRPA-U16 mainboards/the ASUS RS500A-E11-RS12U systems respectively):

module size	2 DIMMs	4 DIMMs	8 DIMMs	16 DIMMs
8 GB	16 GB	32 GB	64 GB	128 GB
16 GB	32 GB	64 GB	128 GB	256 GB
32 GB	64 GB	128 GB	256 GB	512 GB
64 GB	128 GB	256 GB	512 GB	1.024 GB
Assembly	AMD-EPYC-Rome-DIMM-Performance-Single-02-of-16-DIMMs.png	AMD-EPYC-Rome-DIMM-Performance-Single-04-of-16-DIMMs.png	AMD-EPYC-Rome-DIMM-Performance-Single-08-of-16-DIMMs.png	AMD-EPYC-Rome-DIMM-Performance-Single-16-DIMMs.png
Maximum transfer rate	3.200 MT/s	3.200 MT/s	3.200 MT/s	2.933 MT/s (2 DPC)
Maximum memory bandwidth 2))	~28%	~ 54%	~ 100 %	~ 92% (*)

• (*) In the listed test report, 100 per cent are listed. However, the tests have been performed with 2.933 MT/s modules. Compared to 8 x 3,200 MT/s modules, equipping the system with 16 modules results in approximately 92% of the maximum transfer rate, as when using 2 DPC (Dimms per channel) maximum 2.933 MT/s are supported by the CPU. ³⁾

• Memory Population Guidelines for AMD EPYC™ 7003 Series Processors (amd.com)