NEC Express5800 User Manual page 428

9-90 Upgrading Your Server
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.
IMPORTANT: The memory LockStep feature uses channels 0 and 1.
When setting up this feature, memory channel 2 of each CPU
(CPU1-DIMM3/6, CPU2-DIMM3/6) cannot be used. It is necessary to
install an additional N8102-392/393/394/395/396 memory stick.