Lenovo Thinkstation P920 Manual page 8

The following guidelines are recommended by Lenovo for obtaining the best
memory bandwidth from your P720 when filling DIMM slots:
 In single CPU configurations, only DIMM slots for CPU1 can be
utilized. For dual CPU configurations, all DIMM slots can be utilized.
 In dual CPU configurations, it is optimal to balance memory across
CPUs. This applies to both DIMM quantity and capacity. While the
system will function with unbalanced DIMMs, overall memory
performance could be affected.
 For best memory bandwidth performance, Lenovo recommends
optimizing the overall memory configuration to use 6 DIMMs per
CPU.
 Once DIMM quantity and DIMM capacity have been balanced across
CPUs (if necessary), users should follow the recommended fill order
for each CPU found in Figure 4. Largest capacity DIMMs should be
installed first if using mixed DIMM capacities.
Figure 4 shows the recommended DIMM slot fill order for each CPU installed in the
system.
Figure 4 - P720 DIMM Slot Fill Order Recommendations
# of DIMMs per CPU
1 DIMM
2 DIMMs
3 DIMMs
4 DIMMs
5
5 DIMMs
6 DIMMs
Note: Memory configurations using 5 DIMMs per CPU are not recommended as they are
unbalanced configurations that could result in memory performance degradation.
5
- 5 DIMM per CPU configurations will function, but should be avoided as they present an
unbalanced load to the CPU that could result in memory bandwidth degradation.
DIMM slots used for each CPU
DIMM 3
DIMM 3, DIMM 5
DIMM 1, DIMM 3, DIMM 5
DIMM 3, DIMM 4, DIMM 5, DIMM 6
Not Recommended
DIMM 1, DIMM 2, DIMM 3, DIMM 4,
DIMM 5, DIMM 6