Owners Manual

Installing System Components 125
• Two memory modules per channel are limited to 800 MHz,
regardless of memory module speed.
• If quad-rank memory modules are mixed with single- or dual-rank
modules, the quad-rank modules must be installed in the sockets with the
white release levers.
• If memory modules with different speeds are installed, they will operate at
the speed of the slowest installed memory module(s).
Mode-Specific Guidelines
Three memory channels are allocated to each processor. The number of
channels and allowable configurations depend on the memory mode selected.
Advanced ECC (Lockstep) Mode Support
In this configuration, the two channels closest to the processor are combined
to form one 128-bit channel. This mode supports SDDC for both x4- and x8-
based memory modules. Memory modules must be identical in size, speed,
and technology in corresponding slots.
Memory Mirroring Support
The system supports memory mirroring if identical memory modules are
installed in the two channels closest to the processor (memory should not be
installed in the farthest channel). Mirroring must be enabled in the System
Setup program. In a mirrored configuration, the total available system memory
is one-half of the total installed physical memory.
Optimizer (Independent Channel) Mode
In this mode, all three channels are populated with identical memory
modules. This mode permits a larger total memory capacity but does not
support SDDC with x8-based memory modules.
A minimal single-channel configuration of one 1-GB memory module per
processor is also supported in this mode.
Table 3-2 and Table 3-3 show sample memory configurations that follow the
appropriate memory guidelines stated in this section. The samples show
identical memory-module configurations and their the physical and available
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