IBM System x3500 Service Manual page 77

v The server supports up to 12 DIMMs.
v There must be at least one pair of DIMMs installed for the server to operate.
v When you install additional DIMMs, be sure to install them in pairs. All the DIMM
pairs must be the same size and type.
v The server supports online-spare memory. This feature disables the failed
memory from the system configuration and activates an online-spare DIMM to
replace a failed active DIMM. Online-spare memory reduces the amount of
available memory. Each online-spare DIMM must be the same speed, type, and
the same size as, or larger than, the largest active DIMM.
Enable online-spare memory through the Configuration/Setup Utility program.
The BIOS code assigns the online-spare DIMMs according to your DIMM
configuration. Two online-spare configurations are supported.
v You do not have to save new configuration information when you install or
remove DIMMs.
Branch 0
Channel 1
Channel 0
DIMM 3
DIMM 6
DIMM 5 DIMM 2
DIMM 4 DIMM 1
v Two memory branches are split between the 12 DIMM slots. DIMM slots 1
through 6 are on branch 0, and DIMM slots 7 through 12 are on branch 1.
v The server can operate in memory mirroring, non-mirroring (normal), and
online-spare modes. The server can also operate in a single-channel mode when
one DIMM is installed.
v The server supports memory mirroring (mirroring mode) and online-spare
memory.
– Memory mirroring replicates and stores data on DIMMs within two branches
simultaneously. You must enable memory mirroring through the
Configuration/Setup Utility program (see "Using the Configuration/Setup Utility
program" on page 14). To enable memory mirroring in the Configuration/Setup
Utility program, select Devices and I/O Ports → Advanced Chipset Control →
Memory Branch Mode. Use the arrow keys to change the Memory Branch
Mode setting to Mirror; then, save your changes. When you use memory
mirroring, consider the following information:
- The maximum available memory is reduced to 16 GB, instead of the 32 GB
available in non-mirroring mode.
- The minimum memory configuration is four identical DIMMs. You must
install identical pairs of fully buffered, dual-inline memory modules (DIMMs)
in all four DIMM connectors (same size, type, speed, and technology).
These DIMMs must span across both branches and all four channels. For
example, when you install the first four DIMMs, you must install two DIMMs
in branch 0 (one in channel 0 and one in channel 1) and two DIMMs in
branch 1 (one in channel 2 and one in channel 3). See Table 5 on page 68
for the DIMM installation sequence.
- When you upgrade the server to eight DIMMs, the DIMMs that are next to
each other (for example, DIMM connector 1 and DIMM connector 4) within
the channels of a branch must be identical in size, type, speed, and
technology. However, the DIMMs in the connectors above or below each
Branch 1
DIMM 12 DIMM 9
DIMM 11 DIMM 8
DIMM 10 DIMM 7
Chapter 4. Removing and replacing server components
Channel 3
Channel 4
67