Installation and Service Manual

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
specic slot population requirements.
Memory sparing
NOTE: To use memory sparing, this feature must be enabled in BIOS menu of System Setup.
Table 32. Memory sparing
Memory sparing (Single Rank) 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 (Multi Rank) 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.
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 conguration with twenty four 16 GB dual-rank memory modules, the available system memory is: 3/4 (ranks/
channel) × 16 (memory modules) × 16 GB = 192 GB, and not 16 (memory modules) × 16 GB = 256 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 oer protection against a multi-bit uncorrectable error.
Memory mirroring
Memory mirroring oers the strongest memory module reliability mode, providing improved uncorrectable multi-bit failure protection. In a
mirrored conguration, 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 33. Memory population rules
Processor Conguration Memory population Memory population information
Single CPU Optimizer (Independent channel)
population order
1, 2, 3, 4, 5, 6, 7, 8, 9, 10 Populate in this order, odd amount
allowed.
Mirror population order {1, 2, 3, 4, 5, 6} Mirroring is supported with 6 DIMM
slots per CPU.
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.
Installation and Service Manual
Installing and removing system components
99