Intel® Server System S7000FC4UR TPS BIOS Initialization
Revision 1.0
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The underlying assumption is that FBDIMMs generating increasing numbers of ECC
Correctable Errors are eventually prone to ECC Uncorrectable Errors. These FBDIMMs should
be removed from service prior to causing a system crash.
Once a FBDIMM rank exceeds the specified frequency of ECC Correctable Errors the contents
of the failing FBDIMM rank are copied to the spare (reserved) FBDIMM rank. Hardware then
isolates and removes the failing FBDIMM rank from the set of active FBDIMM ranks. These
actions prevent future memory errors and maintain system integrity.
Note: The DIMM sparing feature requires that the spare FBDIMM rank be at least the size of
the largest primary FBDIMM rank in use. When sparing is enabled, the BIOS selects the spare
rank automatically during POST. No manual configuration of this feature is required beyond
turning on the feature in BIOS Setup. With sparing enabled, the total effective memory size is
reduced by the size of the spare FBDIMM rank(s).
14.2.13.3.2 Dual-Ranked DIMM Sparing
When a dual-ranked FBDIMM is used as spare, the BIOS can independently select a physical
rank on that FBDIMM as the spare unit and utilize the other physical rank as a normal unit. This
selective sparing ensures maximization of available memory while still providing RAS.
Note: Populating differently ranked FBDIMMs for sparing is not a good practice and may yield
unpredictable results.
14.2.13.4 Memory Mirroring
The chipset MCH component provides the ability to configure the available set of FBDIMMs in
the mirrored configuration. Unlike memory sparing, the mirrored configuration is a redundant
image of the memory. In addition, the system can generally continue to operate despite the
presence of sporadic ECC Memory Uncorrectable Errors.
Memory mirroring is a RAS feature in which two identical images of memory data are
maintained, providing maximum redundancy. Mirroring is achieved across Branch 0 and Branch
1 such that one of these branches is the primary image and the other the secondary. The
memory controller alternates between both branches for read transactions. Write transactions
are issued to both branches under normal circumstances.
Due to the available system memory being divided into a primary image and a copy of the
image, the effective system memory is reduced by one-half. For example, if the system is
operating in memory mirroring mode and the total size of the FBDIMMs is 1 GB, the effective
size of the memory is 512 MB because half of the FBDIMMs are the secondary images.
For memory mirroring to work, memory riser boards must be installed in pairs and all DIMMs
with the same slot number must match. For e.g. Memory Riser Board A DIMM slot 1 must be
the same as Memory Riser Board B DIMM slot 1. It is not required to match DIMMs between
different slot numbers. DIMMS installed must be the same number of ranks, timing, and size.
The BIOS provides a Setup option to enable memory mirroring. When memory mirroring is
enabled, the BIOS attempts to configure the memory system accordingly. If the FBDIMM
population is not suitable for mirroring, the BIOS disables mirroring. It then reverts to the default
non-RAS mode with maximum interleave or to the single channel mode based on the system
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