System Memory

System memory guidelines

The PowerEdge systems support DDR4 Registered DIMMs (RDIMMs), and Load Reduced DIMMs (LRDIMMs). System memory holds the instructions that are executed by the processor.

Your system contains 16 memory sockets. Processor 1 supports up to 10 memory sockets and Processor 2 supports up to 6 memory sockets. Six memory channels are allocated to each processor. Processor 1 has four 2 DIMM slots per channel and two 1 DIMM slot per channel, Processor 2 has six 1 DIMM per channel.

Memory channels are organized as follows:

Table 1: Memory channels

Processor	Channel 0	Channel 1	Channel 2	Channel 3	Channel 4	Channel 5
Processor 1	Slots A1 and A7	Slots A2 and A8	Slots A3	Slots A4 and A9	Slots A5 and A10	Slots A6
Processor 2	Slots B1	Slots B2	Slots B3	Slots B4	Slots B5	Slots B6

Table 2: Memory population

DIMM Type	DIMMs Populated/ Channel	Voltage	Operating Frequency (in MT/s)	Maximum DIMM Rank/ Channel
RDIMM	1	1.2 V	2666, 2400, 2133, 1866	Dual rank or single rank
RDIMM	2	1.2 V	2666, 2400, 2133, 1866	Dual rank or single rank
LRDIMM	1	1.2 V	2666, 2400, 2133, 1866	Quad rank
LRDIMM	2	1.2 V	2666, 2400, 2133, 1866	Quad rank

General Memory Module Installation Guidelines

To ensure optimal performance of your system, observe the following general guidelines when configuring your system memory. If your system's memory configurations fail to observe these guidelines, your system might not boot, stop responding during memory configuration, or operate with reduced memory.

● System profile selected (for example, Performance Optimized, or Custom [can be run at high speed or lower)

● Maximum supported DIMM speed of the processors.

● Maximum supported speed of the DIMMs

Note: MT/s indicates DIMM speed in MegaTransfers per second.

The system supports Flexible Memory Configuration, enabling the system to be configured and run in any valid chipset architectural configuration. The following are the recommended guidelines for installing memory modules:

● All DIMMs must be DDR4.

● RDIMMs and LRDIMMs must not be mixed.

● 64 GB LRDIMMs that are DDP (Dual Die Package) LRDIMMs must not be mixed with 128 GB LRDIMMs that are TSV (Through Silicon Via/3DS) LRDIMMs.

● x4 and x8 DRAM based memory modules can be mixed.

● Up to two RDIMMs can be populated per channel regardless of rank count.

● Up to two LRDIMMs can be populated per channel regardless of rank count.

● A maximum of two different ranked DIMMs can be populated in a channel regardless of rank count.

● If memory modules with different speeds are installed, they will operate at the speed of the slowest installed memory module(s).

● Populate memory module sockets only if a processor is installed.

For single-processor systems, sockets A1 to A10 are available.

For dual-processor systems, sockets A1 to A10 and sockets B1 to B6 are available.

● Populate all the sockets with white release tabs first, followed by the black release tabs.

● When mixing memory modules with different capacities, populate the sockets with memory modules with the highest capacity first.

Note: For example, if you want to mix 8 GB and 16 GB memory modules, populate 16 GB memory modules in the sockets with white release tabs and 8 GB memory modules in the sockets with black release tabs.

● Memory modules of different capacities can be mixed provided other memory population rules are followed.

Note: For example, 8 GB and 16 GB memory modules can be mixed.

● In a dual-processor configuration, the memory configuration for each processor must be identical.

Note: For example, if you populate socket A1 for processor 1, then populate socket B1 for processor 2, and so on.

● Mixing of more than two memory module capacities in one system is not supported.

● Unbalanced memory configurations will result in a performance loss so always populate memory channels identically with identical DIMMs for best performance.

● Populate six identical memory modules per processor (one DIMM per channel) at a time to maximize performance. DIMM population update for Performance Optimized mode with quantity of 4 and 8 DIMMs per processor.

● When the DIMM quantity is 4 per processor, the population is slot 1, 2, 4, 5.

● When the DIMM quantity is 8 per processor, the population is slot 1, 2, 4, 5, 7, 8, 9, 10.

Mode-specific guidelines

The configurations allowed depend on the memory mode selected in the System BIOS.

Memory Operating Mode	Description
Optimizer Mode	The Optimizer Mode if enabled, the DRAM controllers operate independently in the 64-bit mode and provide optimized memory performance.
Mirror Mode	The Mirror Mode if enabled, the system maintains two identical copies of data in memory, and the total available system memory is one half of the total installed physical memory. Half of the installed memory is used to mirror the active memory modules. This feature provides maximum reliability and enables the system to continue running even during a catastrophic memory failure by switching over to the mirrored copy. The installation guidelines to enable Mirror Mode require that the memory modules be identical in size, speed, and technology, and they must be populated in sets of 6 per processor.
Single Rank Spare Mode	Single Rank Spare Mode allocates one rank per channel as a spare. If excessive correctable errors occur in a rank or channel, while the operating system is running, they are moved to the spare area to prevent errors from causing an uncorrectable failure. Requires two or more ranks to be populated in each channel.
Multi Rank Spare Mode	Multi Rank Spare Mode allocates two ranks per channel as a spare. If excessive correctable errors occur in a rank or channel, while the operating system is running, they are moved to the spare area to prevent errors from causing an uncorrectable failure. Requires three or more ranks to be populated in each channel. With single rank memory sparing enabled, the system memory available to the operating system is reduced by one rank per channel. For example, in a dual-processor configuration with sixteen 16 GB dual-rank memory modules, the available system memory: 16 GB x 16(memory modules) - 8GB(1 rank sparing/channel) x 12(channel) = 256 GB - 96 GB = 160 GB. For multi rank sparing, in a dual-processor configuration with sixteen 64 GB quad-rank memory modules, the available system memory: 64 GB x 16(memory modules) - 32 GB(2 rank sparing/channel) x 12 (channel) = 1024 GB - 384 GB = 640 GB. NOTE: To use memory sparing, this feature must be enabled in the BIOS menu of System Setup. NOTE: Memory sparing does not offer protection against a multi-bit uncorrectable error.
Dell Fault Resilient Mode	The Dell Fault Resilient Mode if enabled, the BIOS creates an area of memory that is fault resilient. This mode can be used by an OS that supports the feature to load critical applications or enables the OS kernel to maximize system availability. This feature is only supported in Gold and Platinum Intel processors. Memory configuration has to be of same size DIMM, speed, and rank.

Optimizer Mode

This mode supports Single Device Data Correction (SDDC) only for memory modules that use x4 device width. It does not impose any specific slot population requirements.

● Dual processor: Populate the slots in round robin sequence starting with processor 1.

Note: Processor 1 and processor 2 population should match.

Processor

Configuration

Memory population

Memory population information

Single processor

Optimizer (Independent channel) population order

1, 2, 3, 4, 5, 6, 7, 8, 9, 10

● Populate in this order, odd amount allowed.

● Odd number of DIMM population is allowed.

Note: NOTE: Odd number of DIMMs will result in unbalanced memory configurations, which in turn will result in performance loss. It is recommended to populate all memory channels identically with identical DIMMs for best performance.

●Optimizer population order is not traditional for 4 and 8 DIMM installations of single processor.

For 4 DIMMs: A1, A2, A4, A5

For 8 DIMMs: A1, A2, A4, A5, A7, A8, A9, A10

Mirror population order

{1, 2, 3, 4, 5, 6}

Mirroring is supported with 6 DIMM slots per processor.

Single rank sparing population order

1, 2, 3, 4, 5, 6, 7, 8, 9, 10

Populate in this order, odd amount allowed. Requires two ranks or more per channel.

Multi rank sparing population order

1, 2, 3, 4, 5, 6, 7, 8, 9, 10

Populate in this order, odd amount allowed. Requires three ranks or more per channel.

Dual processor (Populate round robin starting with processor1)

Optimized (Independent channel) population order

A{1}, B{1}, A{2}, B{2}, A{3}, B{3}...

● Odd amount of DIMM slots per processor allowed.

● Odd number of DIMM population is allowed.

● Optimizer population order is not traditional for 8 and 14 DIMM installations of dual processor.

○ For 8 DIMMs: A1, A2, A4, A5, B1, B2, B4, B5

○ For 14 DIMMs: A1, A2, A4, A5, A7, A8, A9, A10, B1, B2, B3, B4, B5, B6

Mirroring population order

A{1, 2, 3, 4, 5, 6}, B{1, 2, 3, 4,

5, 6}

Mirroring is supported with 6 DIMM slots per processor.

Single rank sparing population order

A{1}, B{1}, A{2}, B{2}, A{3},

B{3}...

Populate in this order, odd amount per processor allowed. Requires

two ranks or more per channel.

Multi rank sparing population

order

A{1}, B{1}, A{2}, B{2}, A{3},

B{3}...

Populate in this order, odd amount per processor allowed. Requires

three ranks or more per channel.