NEC Express5800 Series User Manual page 69

Chapter 2 Preparations
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Memory LockStep Feature (x8 SDDC)
In Memory LockStep feature, the DIMMs in two groups corresponding to two memory channels (channels 2
and 3) is multiplexed and operated in parallel to enable x8 SDDC (x8 Single Device Data Correction). With this
feature, a single device can detect and correct one to eight-bit error.
The LockStep feature can be used under the following conditions:
•
Install two DIMMs that operate in parallel in memory socket.
•
All the installed DIMMs should have the same capacity.
•
Run SETUP (refer to Chapter 2 (1. System BIOS) in "Maintenance Guide"), change parameters
appropriately in the [LockStep] menu selected as shown below, save the settings.
[Advanced] – [Memory Configuration] – [Memory RAS Mode] – [Lock Step]
Run SETUP again, and check if the status of additionally installed DIMMs shows "LockStep".
•
Installation order depends on CPU configuration. See the figure below.
The LockStep cannot be configured in the following cases:
•
LockStep between memory channels of different memory controllers (CPU)
•
LockStep within the same memory channel
Notes on Configuring LockStep
If you install or remove DIMMs that unable to configure Memory LockStep, parameter for [Memory RAS Mode]
is changed from "LockStep" to "Independent".
•
Important
The Memory LockStep feature uses channels 2 and 3. In Memory LockStep
configuration, the memory channel 1 of each CPU (CPU1-DIMM1/4,
CPU2-DIMM1/4) is disabled.
•
To use the Memory LockStep feature, additional memory board
N8102-577/578/579 (equipped with two DIMMs of same model) is required.
Express5800/R120e-1E User's Guide
1. Installing Internal Optional Devices
69