Memory module installation rules and order

Memory modules must be installed in a specific order based on the memory configuration that you implement on your server.

General mixing rules:

DIMMs	Coexist in a channel	Coexist in a system
RDIMMs and Performance+ RDIMMs
3DS RDIMMs and other DIMM types
128 GB 3DS RDIMMs and 256 GB 3DS RDIMMs
DIMMs of different DRAM density (8Gbit and 16 Gbit)	√¹	√¹
DIMMs of different DRAM data width (x4 and x8)		√
DIMMs of different rank	√²	√²
DIMMs manufactured by different vendors	√	√
DIMMs of different voltage³
ECC and Non-ECC DIMMs⁴
Install the one with the higher density first. Install the one with the higher rank first. Only support 1.2 V. Only support ECC DIMMs.

DIMM compatibility (based on general mixing rules)

Type	Option	Capacity	DRAM data width	DRAM density
RDIMM	1	16 GB	x8	8 Gbit
	2	32 GB	x4	8 Gbit
	3	32 GB	x8	16 Gbit
	4	64 GB	x4	16 Gbit
Performance+ RDIMM	5	32 GB	x8	16 Gbit
Performance+ RDIMM	6	64 GB	x4	16 Gbit
3DS RDIMM	7	128 GB	x4	16 Gbit
3DS RDIMM	8	256 GB	x4	16 Gbit
Support mixing within a channel: Options 1 and 3 Options 2 and 4 Support mixing within a system: Options 1 to 4 (Install the one with higher DRAM density first.) Options 5 and 6 (Install the one with higher capacity first.)

Alternatively, for balancing memory and for better performance, consider below rules:

Balance memory capacity per channel pair on a given CPU.
Balance memory capacity per CPU socket when 2 CPUs are installed.
In cases of using Performance+ RDIMMs to maximize memory operating speed, ensure that Performance+ RDIMMs with the same capacity are populated on 2DPC. Otherwise, there will be no performance gain.
When only one DIMM is to be populated in a given channel, it must be populated in DIMM slot 1 (physically farthest away from the CPU).
The server supports single DIMM as a minimum configuration, however, full memory bandwidth requires one DIMM per channel (A–H) be populated. For best performance, populate all 8 channels per socket, with every channel having the same capacity.

Note

Detailed instructions for balancing memory configurations for your server can be found at:

Balanced Memory Configurations with Second-or-Third-Generation AMD EPYC Processors

Recommended population order (based on general rules)

1 CPU installed:

2 CPUs installed:

Note

There are performance-optimized 6-DIMM and 12-DIMM configurations for server models with one 7003 series CPU and 12-DIMM and 24-DIMM configurations for server models with two 7003 series CPUs. For details, see the table below.

CPU Qty.	DIMM Qty.	Performance-optimized DIMM population order
1	6	1, 3, 7, 10, 14, 16
1	12	1, 2, 3, 4, 7, 8, 9, 10, 13, 14, 15, 16
2	12	1, 3, 7, 10, 14, 16, 17, 19, 23, 26, 30, 32
2	24	1, 2, 3, 4, 7, 8, 9, 10, 13, 14, 15, 16, 17, 18, 19, 20, 23, 24, 25, 26, 29, 30, 31, 32

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