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Memory optimized (independent channel) 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.
Memory sparing
NOTE:
To use memory sparing, this feature must be enabled in BIOS menu of System Setup.
Table 40. Memory sparing
Type
Memory sparing (Single Rank)
Memory sparing (Multi Rank)
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 twenty four 16 GB dual-rank memory modules, the available system
memory is: 3/4 (ranks/channel) × 24 (memory modules) × 16 GB = 288 GB, and not 24 (memory modules) × 16 GB = 384 GB.
This calculation changes based on if it is single rank sparing or multi rank sparing. For multi rank sparing, the multiplier changes
to 1/2 (ranks/channel).
NOTE:
Memory sparing does not offer protection against a multi-bit uncorrectable error.
Memory mirroring
Memory mirroring offers the strongest memory module reliability mode, providing improved uncorrectable multi-bit failure
protection. In a mirrored configuration, 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. In the event of an uncorrectable error, the system
switches over to the mirrored copy. This ensures Single Device Data Correction (SDDC) and multi-bit protection.
The installation guidelines for memory modules are as follows:
● Memory modules must be identical in size, speed, and technology.
● Memory modules must be populated in sets of 6 per CPU to enable memory mirroring.
Table 41. Memory population rules
Processor
Configuration
Dual CPU (Starting
Optimized (Independent
with CPU1, CPU1
channel) population order
and CPU2 population
should match)
Removing a memory module
Prerequisites
1. Follow the safety guidelines listed in
2. Follow the procedure listed in
3. If applicable, remove the
Description
Memory sparing allocates one rank per channel as a spare. If excessive
correctable errors occur in a rank or channel, they are moved to the spare
area while the operating system is running to prevent errors from causing an
uncorrectable failure. Requires population of two ranks or more per channel.
Memory sparing allocates two ranks per channel as a spare. If excessive
correctable errors occur in a rank or channel, they are moved to the spare
area while the operating system is running to prevent errors from causing
an uncorrectable failure. Requires population of three ranks or more per
channel.
Safety instructions
Before working inside your system
air
shroud.
Memory population
C1{1}, C2{1}, C1{2}, C2{2},
C1{3}, C2{3}...
on page 55.
on page 56.
Installing and removing system components
Memory population information
Odd amount of DIMMs per CPU
allowed.
71
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