NEC Express5800/R120e-2E User Manual page 73

Chapter 2 Preparations
Notes on Configuring Memory Mirroring
If you install or remove DIMMs that unable to configure memory mirroring, parameter for [Memory RAS Mode] is
changed from "Mirror" to "Independent".
(2) Memory LockStep Feature (x8 SDDC)
In Memory LockStep feature, the DIMMs in two groups corresponding to two memory channels (channels 0 and
1) 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".
• The Memory LockStep feature uses channels 2 and 3. In Memory LockStep
Important
configuration, the memory channel 1 of each CPU (CPU1-DIMM1/4, CPU2-DIMM1/4)
is disabled.
• To use Memory LockStep feature, additional memory board N8102-577/578/579
(equipped with four DIMMs of same model) is required.
Express5800/R120e-2E User's Guide
1. Installing Internal Optional Devices
73