Hardware options installation 43
• DIMMs must be installed in pairs with identical characteristics. When possible, for configuration
simplicity, HP recommends using DIMMs with identical part numbers throughout the system.
• DIMM pairs must be populated in sequence by letter designation. Install DIMM pair (1A, 8A) first,
followed by DIMM pair (3B, 6B), DIMM pair (2C, 7C) and DIMM pair (4D, 5D).
The illustration below represents each processor/cartridge population. This example shows two
cartridges installed behind processor 1 with the associated bus connections and DIMM locations.
• To achieve maximum performance, balance DIMM pairs by letter groupings across all memory
cartridges so that the (1A, 8A) pair is installed in all memory cartridges first, followed by the B-pair,
C-pair, and D-pair.
• When installing mixed rank DIMMs in any cartridge, DIMMs with the highest number of ranks must
be installed in the white DIMM connector locations. This guarantees proper electrical signaling on
the DDR3 channel since DIMMs with higher rank counts present larger electrical loading on the
DDR3 channel and must be populated at the end point of the channel. For more information, see the
illustration below.
CAUTION: Failure to follow these guidelines may result in the inability to recognize memory,
memory errors, or reduced memory performance.
Examples:
o If the configuration is four quad-rank 8-GB DIMMs and four dual-rank 8-GB DIMMs, the quad-
rank DIMMs must be installed in the white DIMM connectors 1A/8A and 3B/6B. The dual-rank
DIMMs must be installed in the black DIMM connectors 2C/7C and 4D/5D. See the figure
below, which illustrates how the processor, memory cartridge, and DIMMs are connected
electronically.
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