Lockstep Memory Mode - IBM System x3850 X6 Installation And Service Manual

Lockstep memory mode

Use this information for notes and details about lockstep memory mode and
DIMM population sequence.
Lockstep memory mode supports the memory mirroring and memory rank sparing
features. When you use lockstep memory mode, consider the following:
v Lockstep memory mode provides the best memory RAS features.
v DIMMs must be installed in pairs across the memory channels (two DIMMs in
v Each pair of DIMMs in the DDR3 channels must be populated with identical
v The memory channel operates at the DDR3 channel transfer rate.
v The amount of memory installed in lockstep memory mode is the amount of
v
For more information about the DIMM population sequence for lockstep memory
mode, see "Memory mirroring in lockstep mode" on page 60 and "Memory rank
sparing in lockstep mode" on page 62. For more information and notes about
installing DIMMs, see "Installing a memory module" on page 47..
The following table lists the maximum memory speed supported based on the type
of ranked DIMM and the voltage at which the DIMM runs.
Note: The DIMM operating speed and voltage can vary depending on the
microprocessor installed, memory installed, and performance mode that is set in
the Setup Utility.
Table 14. Memory speeds and configurations based on ranked DIMM type and voltage for lockstep memory mode
DIMM rank,
type, and DIMM
technology capacity
Single-rank x4 4 GB
RDIMM - 2 Gb
(1600 MHz)
Single-rank x4 8 GB
RDIMM - 4 Gb
(1600 MHz)
Dual-rank x4 16 GB
RDIMM - 4 Gb
(1600 MHz)
Quad-rank x4 32 GB
LRDIMM - 4 Gb
(1600 MHz)
Octal-rank x4 64 GB
(8-rank) LRDIMM
- 4 Gb (1333
MHz)
each memory channel), alternating between the DDR3 channels.
DIMMs. That is, the DIMMs must be identical in size, organization, etc.. For
example, the DIMMs in slots 9 (DDR3 channel 0) and 15 (DDR3 channel 1) must
be identical.
memory that is available for use.
1 DIMM per DDR3
channel
1.35 V 1.50 V
1333 1600
1333 1600
1333 1600
1333 1600
1333 1333
2 DIMMs per DDR3
channel
1.35 V 1.50 V
1333 1600
1333 1600
1333 1600
1333 1600
1333 1333
Chapter 2. Installing optional devices
3 DIMMs per DDR3
channel
1.35 V 1.50 V
1066 1333
1066 1333
1066 1333
1333 1333
1333 1333
59