Dell POWEREDGE 1955 - Manual (Page 78)

78
Installing System Options
The eight memory module sockets are divided into two equal branches (0 and 1). Each branch consists
of two channels:
• Branch 0: Channel 0 (DIMM 1, DIMM 5) and channel 1 (DIMM 2, DIMM 6)
• Branch 1: Channel 2 (DIMM 3, DIMM 7) and channel 3 (DIMM 4, DIMM 8)
The first socket of each channel has white release tabs. The memory sockets are located on the system
board at the back of the server module. See Figure 6-3 in "Server Module Board Connectors.
General Memory Module Installation Guidelines
• In memory configurations where sparing and mirroring are not supported, the memory modules must
be installed in pairs of matched memory size, speed, technology, and vendor, beginning with Branch 0
(Channel 0 and Channel 1).
• The system supports memory mirroring and memory sparing. (Only one of these features can be
implemented at one time.) See"Memory Sparing" on page 78 and "Memory Mirroring" on page 79.
• The system supports both single-ranked and dual-ranked memory modules. (Memory modules marked
with a "1R" are single ranked and modules marked with a "2R" are dual ranked.) If you install both
single-ranked and dual-ranked memory modules, the dual-ranked memory modules must be installed
in Branch 1, regardless of capacity.
NOTE:
Dual-rank memory modules with less capacity take precedence over single-ranked memory modules
with greater capacity.
NOTICE:
For configurations requiring less than eight memory modules, memory module blanks must be installed in
four of the unoccupied memory sockets to maintain proper cooling airflow. See Table 3-2.
Memory Sparing
Memory sparing allocates four ranks of memory to a spare bank. These four ranks consist of the first rank
of memory in sockets 1 through 4.
• For single-rank memory modules, the entire capacity of the memory modules is allocated to sparing.
• For dual-rank memory modules, only half of the total capacity is allocated to sparing.
Table 3-1 shows how memory sparing divides the available and spared memory in each of the single- and
dual-ranked memory module combinations.