Lenovo 6241, Installation And Service Manual

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Notes:
– When one DIMM per compute book is installed, system performance can be slow.
– For best performance, install DIMMs evenly across all four memory channels for each compute book.
• The server supports two operating modes, independent memory mode and lockstep memory mode. Both
modes support memory-mirroring and memory rank sparing . For more information about memory
mirroring, see “Memory mirroring” on page 52. For more information about memory rank sparing, see
“Memory rank sparing” on page 52.
– Independent memory mode: This mode provides the most efficient performance. It supports single-
device data correction (SDDC) for x4 SDRAM technology. All cache lines are handled on an individual
basis by the memory controller. Each DDR3 or DDR4 channel provides 8 x 8 byte data transfers (64
byte cache line is provided per channel). For more information on the independent memory mode, see
“Independent memory mode” on page 53.
– Lockstep memory mode: This mode provides the best memory RAS features. It supports dual-device
data correction (DDDC) for x4 SDRAM technology. The memory controller handles all cache lines
across the two DDR3 or DDR4 channels (Channel 0 and Channel 1) on each memory channel. Each
DDR3 or DDR4 channel provides 4 x 8 byte data transfers (64 byte cache line is provided per channel
pair). For more information about the lockstep memory mode, see “Lockstep memory mode” on page
57.
For more information and DIMM population sequence for independent memory mode, see “Memory
mirroring in independent memory mode” on page 54 and “Memory rank sparing in independent mode” on
page 55. For more information and DIMM population sequence for lockstep memory mode, see “Memory
mirroring in lockstep mode” on page 58 and “Memory rank sparing in lockstep mode” on page 59.
eXFlash DIMMs
This topic provides information about eXFlash DIMM installation and requirements.
The Lenovo System x3850 X6 and x3950 X6 server provides support for eXFlash™ DIMMs. You can use
eXFlash DIMMs in unused DIMM slots for solid state drive storage on the server. For more information and
notes about installing DIMMs, see “Installing a memory module” on page 46. eXFlash DIMMs are only
supported in Independent memory mode. For more information about DIMM installation sequence for
Independent memory mode, see “Independent memory mode” on page 53. The DIMM installation order for
eXFlash DIMMs follows the independent mode (performance) installation order.
When you install an eXFlash DIMM, consider the following information:
• RDIMMs must be installed in the server with eXFlash DIMMs. You cannot install all eXFlash DIMMs in the
server.
• RDIMMs must be installed first, then eXFlash DIMMs can be installed.
• When you install eXFlash DIMMs, do not leave an empty DIMM slot between installed DIMMs.
• For both the 4-socket and 8-socket configurations, one eXFlash DIMM can be installed in each DDR3 or
DDR4 channel. A maximum of 8 eXFlash DIMMs can be installed in each compute book. A maximum of 32
eXFlash DIMMs can be installed in the server. In the 8-socket configuration of the server, the eXFlash
DIMMs must be installed in the bottom node only.
• Mixing of LRDIMMs and eXFlash DIMMs in the same server is not supported.
• eXFlash DIMMs are supported in Independent memory mode only.
• eXFlash DIMMs are not supported in Lockstep memory mode, memory mirroring, or memory rank
sparing.
• You can install any configuration of the supported eXFlash DIMMs (up to 32 eXFlash DIMMs) in the server.
• The same level of firmware should be installed on all eXFlash DIMMs in the server.
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System x3850 X6 and x3950 X6 Installation and Service Guide