Owners Manual

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 42. Memory population rules
Processor Configuration Memory population Memory population information
Dual CPU (Starting
with CPU1, CPU1
and CPU2 population
should match)
Optimized (Independent
channel) population order
C1{1}, C2{1}, C1{2}, C2{2},
C1{3}, C2{3}...
Odd amount of DIMMs per CPU
allowed.
Removing a memory module
Prerequisites
1. Follow the safety guidelines listed in Safety instructions on page 56.
2. Follow the procedure listed in Before working inside your system on page 57.
3. If applicable, remove the air shroud.
WARNING:
Allow the memory modules to cool after you power off the system. Handle the memory modules by
the card edges and avoid touching the components or metallic contacts on the memory module.
CAUTION: To ensure proper system cooling, memory module blanks must be installed in any memory socket that
is not occupied. Remove memory module blanks only if you intend to install memory modules in those sockets.
NOTE: You must follow the thermal restriction while using DIMM blank. For information about thermal restriction, see
Thermal restrictions.
Steps
1. Locate the appropriate memory module socket.
CAUTION:
Handle each memory module only by the card edges, ensuring not to touch the middle of the
memory module or metallic contacts.
2. Push the ejectors outward on both ends of the memory module socket to release the memory module from the socket.
3. Lift and remove the memory module from the system.
Installing and removing system components
83