User Guide

Hardware options installation 44
• FBDIMMS must be ECC Registered DDR-2 SDRAM FBDIMMs.
• FBDIMMs must be installed in pairs.
• FBDIMM pairs in a memory bank must have identical HP part numbers.
• FBDIMMS must be populated as specified for each AMP memory mode.
The memory subsystem for this server is divided into two branches. Each memory branch is essentially a
separate memory controller. The FBDIMMs map to the two branches as indicated in the following table:
Branch 0 Branch 1
FBDIMM 1A FBDIMM 5B
FBDIMM 3A FBDIMM 7B
FBDIMM 2C FBDIMM 6D
FBDIMM 4C FBDIMM 8D
This multi-branch architecture provides enhanced performance in Advanced ECC mode. The concept of
multiple branches is important for the operation of online spare mode and mirrored memory mode.
If the server contains more than 4 GB of memory, consult the operating system documentation about
accessing the full amount of installed memory.
Advanced ECC memory
Advanced ECC memory is the default memory protection mode for this server. In Advanced ECC, the
server is protected against correctable memory errors. The server provides notification if the level of
correctable errors exceeds a pre-defined threshold rate. The server does not fail because of correctable
memory errors. Advanced ECC provides additional protection over Standard ECC because it is possible
to correct certain memory errors that would otherwise be uncorrectable and result in a server failure.
Whereas standard ECC can correct single-bit memory errors, Advanced ECC can correct single-bit
memory errors and multi-bit memory errors if all failed bits are on the same DRAM device on the
FBDIMM.
In addition to general configuration requirements, Advanced ECC memory also has the following
configuration requirements:
• FBDIMMs must be installed in pairs.
• FBDIMMs must be installed in sequential order, beginning with bank A.
In Advanced ECC mode, FBDIMMs must be populated as specified in the following table:
Configuration Bank A
1A and 3A
Bank B
5B and 7B
Bank C
2C and 4C
Bank D
6D and 8D
1 X — — —
2 X X — —
3 X X X —
4 X X X X
Online spare memory configuration
Online spare memory provides protection against degrading FBDIMMs by reducing the likelihood of
uncorrectable memory errors. This protection is available without any operating system support.
An understanding of single-rank and dual-rank FBDIMMs is required to understand memory usage in
online spare mode. FBDIMMs can either be single-rank or dual-rank. Certain FBDIMM configuration