Lenovo THINKSERVER 3821 - Manual (Page 220)

v The server supports 1 GB, 2 GB, and 4 GB DIMMs, with a minimum of 1 GB and
a maximum of 64 GB of system memory.
For 32-bit operating systems only: Some memory is reserved for various
system resources and is unavailable to the operating system. The amount of
memory that is reserved for system resources depends on the operating system,
the configuration of the server, and the configured PCI devices.
v The maximum operating speed of the server is determined by the slowest DIMM
in the server.
v The server can operate in two major modes: mirroring and independent channel
modes.
Independent channel mode
The server requires at least one installed DIMM per microprocessor. The server
comes with a minimum of two 1 GB DIMMs, installed in connectors 3 and 6.
Connector 3 (in channel 0) and connector 6 (in channel 1) are the farthest
connectors from microprocessor 1 in those channels. When you install additional
DIMMs, install them in the order shown in Table 11, to maintain server performance.
Note: If you have configured the server to use memory mirroring, do not use the
order shown in this table; go to Table 13 on page 214 and use the installation order
shown there.
Table 11. DIMM installation sequence for independent channel mode
Installed microprocessors DIMM connector population sequence
Microprocessor 1 3, 6, 8, 2, 5, 7, 1, 4
Microprocessor 2 11, 14, 16, 10, 13, 15, 9, 12
Memory mirroring mode
Memory-mirroring mode replicates and stores data on two pairs of DIMMs within
two channels simultaneously. If a failure occurs, the memory controller switches
from the primary pair of memory DIMMs to the backup pair of DIMMs. You must
enable memory mirroring through the Setup Utility. For details about enabling
memory mirroring, see “Using the Setup Utility” on page 252. When you use the
memory mirroring feature, consider the following information:
v When you use memory mirroring, you must install a pair of DIMMs at a time.
One DIMM must be in channel 0, and the mirroring DIMM must be in the same
connector in channel 1. The two DIMMs in each pair must be identical in size,
type, rank (single, dual, or quad), and organization. They do not have to be
identical in speed. The channels run at the speed of the slowest DIMM in any of
the channels. See Table 13 on page 214 for the DIMM connectors that are in
each pair.
v Channel 2, DIMM connectors 7, 8, 15, and 16 are not used in memory-mirroring
mode.
v The maximum available memory is reduced to half of the installed memory when
memory mirroring is enabled. For example, if you install 64 GB of memory, only
32 GB of addressable memory is available when you use memory mirroring.
The following illustration shows the memory channel interface layout with the DIMM
installation sequence for mirroring mode. The numbers within the boxes indicate the
DIMM population sequence in pairs within the channels, and the numbers next to
the boxes indicate the DIMM connectors within the channels. For example, the
212 ThinkServer TD200x Types 3719, 3821, 3822, and 3823: Hardware Maintenance Manual