Hardware options installation 42
Online spare memory protection dedicates one rank of each memory channel for use as spare memory.
The remaining ranks are available for OS and application use. If correctable memory errors occur at a
rate higher than a specific threshold on any of the non-spare ranks, the server automatically copies the
memory contents of the degraded rank to the online spare rank. The server then deactivates the failing
rank and automatically switches over to the online spare rank.
Mirrored memory configuration
Mirroring provides protection against uncorrected memory errors that would otherwise result in server
downtime. Mirroring is performed at the channel level. Channels 1 and 2 are used; channel 3 is not
populated.
Data is written to both memory channels. Data is read from one of the two memory channels. If an
uncorrectable error is detected in the active memory channel, data is retrieved from the mirror channel.
This channel becomes the new active channel, and the system disables the channel with the failed DIMM.
General DIMM slot population guidelines
Observe the following guidelines for all AMP modes:
• Populate DIMM slots for a processor only if the processor is installed.
• To maximize performance in multi-processor configurations, distribute the total memory capacity
between all processors as evenly as possible.
• Do not mix Unbuffered and Registered PC3 DIMMs.
• Each channel supports up to two Unbuffered DIMMs.
• If quad-rank DIMMs are installed for a processor, a maximum of two DIMMs can be installed on
each channel for that processor.
• If a channel contains quad-rank DIMMs, the quad-rank DIMM must be installed first on that channel.
DIMM speeds are supported as indicated in the following table.
Populated slots
(per channel)
Rank
Speeds supported
(MHz)
1 Single- or dual-rank 1333, 1066
1 Quad-rank 1066
2 Single- or dual-rank 1066
3 Single- or dual-rank 800
Advanced ECC population guidelines
For Advanced ECC mode configurations, observe the following guidelines:
• Observe the general DIMM slot population guidelines (on page 42).
• DIMMs may be installed individually.
Single-processor Advanced ECC population order
For Advanced ECC mode configurations with a single processor, populate the DIMM slots in the following
order:
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