Hardware Options Installation 51
Single- and Dual-Rank DIMMs
PC2-3200 DIMMs can either be single- or dual-rank. While it is not normally
important for you to differentiate between these two types of DIMMs, certain
DIMM configuration requirements are based on these classifications.
Certain configuration requirements exist with single- and dual-rank DIMMs that
allow the architecture to optimize performance. A dual-rank DIMM is similar to
having two separate DIMMs on the same module. Although only a single DIMM
module, a dual-rank DIMM acts as if it were two separate DIMMs. The primary
reason for the existence of dual-rank DIMMs is to provide the largest capacity
DIMM given the current DIMM technology. If the maximum DIMM technology
allows for creating 2-GB single-rank DIMMs, a dual-rank DIMM using the same
technology would be 4-GB.
Understanding the existence of single- and dual-rank DIMMs is all that is
necessary for understanding the memory population guidelines of this server.
Online Spare Memory Configuration
In the online spare configuration, the ROM automatically configures the last
populated bank as the spare memory. If only banks A and B are populated,
bank B is the spare bank. If banks A, B, and C are populated, bank C is the spare
bank. If DIMMs in a non-spare bank exceed the limit for the single-bit
correctable errors threshold as defined by the Pre-Failure Warranty, the system
copies the memory contents of the failing bank to the spare bank. The system
then deactivates the failing bank and automatically switches over to the spare
bank.
For online spare memory support, DIMMs installed in the spare bank must be of
equal or greater capacity than the DIMMs installed in other banks.
For example, if bank A is populated with two 512-MB DIMMs and bank B is
populated with two 1-GB DIMMs, bank C must be populated with two 1-GB or
greater DIMMs in order for online spare memory support to function properly.
The following guidelines apply to Online Spare Memory configuration:
• Online Spare Memory requires all DIMMs to be single-rank. ROM will
display an error if any dual-rank DIMMs are installed.
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