Single-, Dual-, And Quad-Rank Dimms; Dimm Identification - HP ProLiant DL120 User Manual

DIMM slots in this server are identified by number and by letter. Letters identify the slots to populate for
specific AMP modes. Slot numbers are reported by ROM messages during boot and for error reporting.

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

IMPORTANT:
these two types causes the server to halt during BIOS initialization.
The memory subsystem may be populated with either RDIMMs or UDIMMs, but mixing the two types is not
supported. To determine DIMM characteristics, use the label attached to the DIMM and the following
illustration and table.
Item Description
Size
1
Rank
2
Data width
3
This server does not support mixing RDIMMs and UDIMMs. Attempting to mix
Definition
—
1R = Single-rank
2R = Dual-rank
4R = Quad-rank
x4 = 4-bit
x8 = 8-bit
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