Hardware options installation 46
3
— 3 mixed SR 1333 MHz
DR 1333 MHz
DR 1066 MHz
1066 MHz 800 MHz
3
1 2 SR 1333 MHz
DR 1333 MHz
DR 1066 MHz
QR 1066 MHz
800 MHz 667 MHz
o 800 MHz—The memory bus speed is set to 800 MHz regardless of the quantity of memory modules
installed, unless the table above reflects a slower memory bus speed.
NOTE: There may be more than one memory bus speed menu option.
Single-, dual-, and quad-rank DIMMs
To understand and configure memory protection modes properly, an understanding of single-, dual-, and
quad-rank DIMMs is helpful. Some DIMM configuration requirements are based on these classifications.
A single-rank DIMM has one set of memory chips that is accessed while writing to or reading from the
memory. A dual-rank DIMM is similar to having two single-rank DIMMs on the same module, with only one
rank accessible at a time. A quad-rank DIMM is, effectively, two dual-rank DIMMs on the same module. Only
one rank is accessible at a time. The server memory control subsystem selects the proper rank within the
DIMM when writing to or reading from the DIMM.
Dual- and quad-rank DIMMs provide the greatest capacity with the existing memory technology. For
example, if current DRAM technology supports 2-GB single-rank DIMMs, a dual-rank DIMM would be 4-GB,
and a quad-rank DIMM would be 8-GB.
DIMM identification
To determine DIMM characteristics, use the label attached to the DIMM and the following illustration and
table.
