NEC Express5800 Series User Manual page 75

Chapter 2 Preparations
The following Memory Sparing cannot be configured.

A DIMM of different model number is installed.

Memory Sparing with different memory channels
Notes on Configuring Memory Sparing
If you additionally install or remove DIMMs that unable to configure Memory Sparing configuration, Memory
RAS Mode is changed to "Independent".
"Spared" is removed from Advanced  Memory Configuration  Memory Information  CPUx_DIMMx
Status xxxx MB (Spared) in BIOS SETUP.
Express5800/T120g User's Guide
1. Installing Internal Optional Devices
75