Acer AR180 F1 Series User Manual page 64

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Lockstep mode
• In lockstep channel mode, each memory access is a 128-bit data
access that spans Channel 1 and Channel 2. This is done to support
SDDC for DRAM devices with 8-bit wide data ports. The same
address is used on both channels such that an address error on any
channel is detectable by ECC. Lockstep Channel mode is the only
RAS mode that supports x8 SDDC.
• Channel 3 has no function and cannot be populated in this mode.
• Follow the population rules described in independent mode.
• DIMM modules installed in channels 1 and 2 must be identical —
1A and 2A should be the same type, size and manufacturer. 1B and
2B memory should be the same type, size and manufacturer.
However, it is not necessary for slot A to have the same memory
module as slot B within a channel.
• The same rule applies to processor 2.
Memory population for lockstep mode
Single processor configuration
Configuration
A
B
Dual processor configuration
Channel 1
Configuration 1B
A
B
C X
D X
Notes: 1. Place DIMMs in "X" location.
2. DIMM population must correspond to the above tables.
3. DIMM modules support 1 GB, 2 GB, 4 GB and 8 GB
DIMMS.
Single processor
Processor 1 P1DIMM slots
Channel 1 Channel 2
1B 1A 2B
X
X X X
Dual processors
Processor 1 P1DIMM slots
Channel 2 Channel 3
1A 2B 2A 3B
X X NA
X X NA
X X X NA
X X X NA
3 System upgrades
Channel 3
2A 3B 3A
X NA NA
X NA NA
Processor 2 P2DIMM slots
Channel 1 Channel 2
3A 1B 1A 2B
NA
NA X
NA X
NA X X X
Channel 3
2A 3B 3A
NA NA
X NA NA
X NA NA
X NA NA