Cisco UCS C240 M3 High-Density Rack Server (Small Form Factor Disk Drive Model)
16
CONFIGURING the SERVER
Caveats
■
For optimum performance:
— Populate at least one DIMM per memory channel per CPU
— Do not mix DIMMs with different voltages, frequencies, or types (registered and
unregistered). If you mix 1.35 V and 1.5 V DIMMs, the system defaults to the 1.5 V
mode. If you mix DIMM frequencies, the system defaults to the lower frequency.
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DIMMs for CPU 1 and CPU 2 (when populated) must always be configured identically.
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Memory mirroring reduces the amount of available memory by 50% (quantity of DIMMs must
be even for mirroring).
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When single- and dual-rank DIMMs are populated for 3DPC, always populate the dual-rank
DIMM in the blue DIMM slot first (blue slot) and the single-rank DIMM last in the black DIMM
slots (only the 4GB DIMMs are single-rank; all other DIMMs that Cisco offers on this server are
dual-rank).
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By default, all DIMMs run at 1.35 V, which yields 1333-MHz memory speeds. To run the
memory DIMMS at 1600 MHz, you need to go into the BIOS or set the policy with UCSM
(service profile) to run in Performance Mode. This forces the DIMMs to operate at 1.5 V and
yields 1600-MHz speeds, provided:
— The DIMMs are 1600-MHz devices
— The CPUs chosen support 1600-MHz operation
— There are less than 3 DIMMs per channel
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With 3 DIMMs populated per channel, memory always runs at 1.5 V regardless if the BIOS
setting is low-power mode (1.35 V) or performance mode (1.5 V).
For more information regarding memory, see
CPUs and DIMMs, page 48
.
NOTE:
Memory speed is limited to 1066 MHz for 3 DPC configurations.