Chapter 3 Maintaining the Server
Installing or Replacing Server Components
Enabling Low-Voltage DIMM Operation
You can enable low voltage (1.35 V) DIMM operation for all DIMMs in the server. There is a setting in the BIOS Setup utility that you can use to change the DDR memory mode to Power Saving mode, as described in the following procedure:
Step 1 Enter the BIOS setup utility by pressing the F2 key when prompted during bootup.
Step 2 Select the Advanced tab.
Step 3 Select Low Voltage DDR Mode.
Step 4 In the
•Power Saving
•Performance
Step 5 Press F10 to save your changes and exit the setup utility.
Memory Mirroring
When memory mirroring is enabled, the memory subsystem simultaneously writes identical data to two channels. If a memory read from one of the channels returns incorrect data due to an uncorrectable memory error, the system automatically retrieves the data from the other channel. A transient or soft error in one channel does not affect the mirrored data, and operation continues unless there is a simultaneous error in exactly the same location on a DIMM and its mirrored DIMM. Memory mirroring reduces the amount of memory available to the operating system by 50% because only one of the two populated channels provides data.
If you choose to enable memory mirroring, population is different for
Table
Number of DIMMs |
|
| |
per CPU |
| CPU 1 Population | CPU2 Population |
|
|
|
|
2 |
| A1; B1 | CPU2 slots not available |
|
|
|
|
4 |
| A1, B1; A2, B2 | CPU2 slots not available |
|
|
|
|
Table | Memory Mirroring DIMM Population, Two CPUs | ||
|
| ||
Number of DIMMs |
|
| |
per CPU |
| CPU 1 Population | CPU2 Population |
|
|
|
|
2 |
| A1; B1 | D1; E1 |
|
|
|
|
4 |
| A1, B1; A2, B2 | D1, E1; D2, E2 |
|
|
|
|
| Cisco UCS C22 Server Installation and Service Guide |
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