Dell PowerEdge T420, Owner'S Manual

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Memory Mirroring
Memory Mirroring offers the strongest DIMM reliability mode compared to all other modes, providing improved
uncorrectable multi-bit failure protection. In a mirrored configuration, the total available system memory is one half of
the total installed physical memory. Half of the installed memory is used to mirror the active DIMMs. In the event of an
uncorrectable error, the system will switch over to the mirrored copy. This ensures SDDC and multi-bit protection.
Memory installation guidelines:
NOTE: The first memory channel for each processor (Channel 1) is disabled and not available for Memory
Mirroring.
• Memory channels 2 and 3 must be populated.
• Memory modules must be identical in size, speed, and technology.
• DIMMs installed in memory sockets with white release tabs must be identical and similar rule applies for sockets
with black release tabs. For example, DIMMs installed in sockets A2 and A3 must be identical.
Sample Memory Configurations
The following tables show sample memory configurations that follow the appropriate memory guidelines stated in this
section.
NOTE: 16 GB quad-rank RDIMMs are not supported.
NOTE: 1R, 2R, and 4R in the following tables indicate single-, dual-, and quad-rank DIMMs respectively.
Table 1. Memory Configurations — Single Processor
System Capacity
(in GB)
DIMM Size (in
GB)
Number of
DIMMs
Organization and
Speed
DIMM Slot Population
2 2 1
1R x8, 1333 MT/s
1R x8, 1600 MT/s
A1
4 2 2
1R x8, 1333 MT/s
1R x8, 1600 MT/s
A1, A2
10 2 5
1R x8, 1333 MT/s
1R x8, 1600 MT/s
A1, A2, A3, A4, A5
12 4 3
1R x8, 1333 MT/s
1R x8, 1600 MT/s
A1, A2, A3
20 4 5
1R x8, 1333 MT/s
1R x8, 1600 MT/s
A1, A2, A3, A4, A5
24 8 3
2R x4, 1333 MT/s
2R x4, 1600 MT/s
A1, A2, A3
32 8 4
2R x4, 1333 MT/s
2R x4, 1600 MT/s
A1, A2, A3, A4
48 16 3
2R x4, 1333 MT/s
2R x4, 1600 MT/s
A1, A2, A3
96 16 6
2R x4, 1333 MT/s
2R x4, 1600 MT/s
A1, A2, A3, A4, A5, A6
128 32 4
4R x4, 1066 MT/s
A1, A2, A3, A4
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