Memory module installation rules

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

Your server supports up to 6 memory modules when one processor is installed, and up to 12 memory modules when two processors are installed. It supports the following types of memory modules depending on the processors installed:

For Intel Xeon SP Gen 1 processors

• Minimum: 8 GB

• Maximum:

  • 384 GB using registered DIMMs (RDIMMs)

  • 768 GB using load-reduced DIMMs (LRDIMMs)

• Type (depending on the model):

  • TruDDR4 2666, single-rank or dual-rank, 8 GB/16 GB/32 GB RDIMMs

  • TruDDR4 2666, quad-rank, 64 GB LRDIMMs

• Slots: 12 slots

For Intel Xeon SP Gen 2 processors

• Minimum: 8 GB

• Maximum: 768 GB

• Type (depending on the model):

  • TruDDR4 2666, single-rank or dual-rank, 16 GB/32 GB RDIMMs

  • TruDDR4 2933, single-rank or dual-rank, 8 GB/16 GB/32 GB/64 GB RDIMMs

• Slots: 12 slots

Note

List of supported memory module is different for 1st generation (Skylake) and 2nd generation (Cascade Lake) Intel Xeon processors. Make sure to install compatible memory modules to avoid system error.For a list of supported DIMMs, see: Lenovo ServerProven website.

Note

Before installing a memory module, ensure that all memory modules to be installed must be the same type. Your server supports the following types of memory modules:

• DDR4 RDIMM with ECC technology

• DDR4 LRDIMM with ECC technology

The following illustration helps you to locate the memory module slots on the system board.

Figure 1. Memory module slots on the system board

The following memory configurations are available:

• Independent mode

• Mirroring mode

• Rank sparing mode

Independent mode

Independent mode provides high performance memory capability. You can populate all channels with no matching requirements. Individual channels can run at different memory module timings, but all channels must run at the same interface frequency.

The following table shows the memory module population sequence for independent mode when only one processor (CPU1) is installed.

Note

If there are three identical memory modules to be installed for CPU1, and the three memory modules have the same Lenovo part number, install the three memory modules in slots 1, 2, and 3.

Table 1. Independent mode with one processor

Total memory modules	Processor 1						Total memory modules
	6	5	4	3	2	1
1				3			1
2			4	3			2
3			4	3	2		3
4		5	4	3	2		4
5		5	4	3	2	1	5
6	6	5	4	3	2	1	6

The following table shows the memory module population sequence for independent mode when two processors (CPU1 and CPU2) are installed.

Note

• If there are three identical memory modules to be installed for CPU1, and the three memory modules have the same Lenovo part number, install the three memory modules in slots 1, 2, and 3.

• If there are three identical memory modules to be installed for CPU2, and the three memory modules have the same Lenovo part numbers, install the three memory modules in slots 7, 8, and 9.

Table 2. Independent mode with two processors

Total memory modules	Processor 2						Processor 1						Total memory modules
	12	11	10	9	8	7	6	5	4	3	2	1
2				9						3			2
3				9					4	3			3
4			10	9					4	3			4
5			10	9					4	3	2		5
6			10	9	8				4	3	2		6
7			10	9	8			5	4	3	2		7
8		11	10	9	8			5	4	3	2		8
9		11	10	9	8			5	4	3	2	1	9
10		11	10	9	8	7		5	4	3	2	1	10
11		11	10	9	8	7	6	5	4	3	2	1	11
12	12	11	10	9	8	7	6	5	4	3	2	1	12

Mirroring mode

In mirroring mode, each memory module in a pair must be identical in size and architecture. The channels are grouped in pairs with each channel receiving the same data. One channel is used as a backup of the other, which provides redundancy.

Note

• All memory modules to be installed must be the same type with the same capacity, frequency, voltage, and rank.

• Partial Memory Mirroring is a sub-function of memory mirroring. It requires following the memory installation order of memory mirroring mode.

The following table shows the memory module population sequence for mirroring mode when one processor (CPU1) is installed.

Table 3. Mirroring mode with one processor

Total memory modules	Processor 1						Total memory modules
	6	5	4	3	2	1
2				3	2		2
3				3	2	1	3
4		5	4	3	2		4
6	6	5	4	3	2	1	6

The following table shows the memory module population sequence for mirroring mode when two processors (CPU1 and CPU2) are installed.

Table 4. Mirroring mode with two processors

Total memory modules	Processor 2						Processor 2						Total memory modules
	12	11	10	9	8	7	6	5	4	3	2	1
4				9	8					3	2		4
5				9	8					3	2	1	5
6				9	8	7				3	2	1	6
8		11	10	9	8			5	4	3	2		8
9				9	8	7	6	5	4	3	2	1	9
10		11	10	9	8		6	5	4	3	2	1	10
12	12	11	10	9	8	7	6	5	4	3	2	1	12

Rank sparing mode

In rank sparing mode, one rank of a memory module works as the spare rank for the other ranks on the same channel. The spare rank is not available as system memory.

Note

• All memory modules to be installed must be the same type with the same capacity, frequency, voltage, and number of ranks.

• Single-rank memory modules do not support rank sparing mode.

Table 5. Rank sparing mode with one processor

Total memory modules	Processor 1						Total memory modules
	6	5	4	3	2	1
1				3			1
2			4	3			2
3			4	3	2		3
4		5	4	3	2		4
5		5	4	3	2	1	5
6	6	5	4	3	2	1	6

The following table shows the memory module population sequence for rank sparing mode when two processors (CPU1 and CPU2) are installed.

Table 6. Rank sparing mode with two processors

Total memory modules	Processor 2						Processor 1						Total memory modules
	12	11	10	9	8	7	6	5	4	3	2	1
2				9						3			2
3				9					4	3			3
4			10	9					4	3			4
5			10	9					4	3	2		5
6			10	9	8				4	3	2		6
7			10	9	8			5	4	3	2		7
8		11	10	9	8			5	4	3	2		8
9		11	10	9	8			5	4	3	2	1	9
10		11	10	9	8	7		5	4	3	2	1	10
11		11	10	9	8	7	6	5	4	3	2	1	11
12	12	11	10	9	8	7	6	5	4	3	2	1	12