HP ProLiant DL380p HP ProLiant DL380p Gen8 Server User Guide - Page 49

DIMM identification, Description, Definition

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Dual- and quad-rank DIMMs provide the greatest capacity with the existing memory technology. For example, if current DRAM technology supports 8-GB single-rank DIMMs, a dual-rank DIMM would be 16 GB, and a quad-rank DIMM would be 32 GB. LRDIMMs are labeled as quad-rank DIMMs; however, they function more like dual-rank DIMMs. There are four ranks of DRAM on the DIMM, but the LRDIMM buffer creates an abstraction that allows the DIMM to appear as a dual-rank DIMM to the system. The LRDIMM buffer also isolates the electrical loading of the DRAM from the system to allow for faster operation. These two changes allow the system to support up to three LRDIMMs per memory channel, providing for up to 50% greater memory capacity and higher memory operating speed compared to quad-rank RDIMMs. DIMM identification To determine DIMM characteristics, use the label attached to the DIMM and the following illustration and table. Item Description 1 Size 2 Rank 3 Data width 4 Voltage rating 5 Memory speed 6 DIMM type Definition - 1R = Single-rank 2R = Dual-rank 4R = Quad-rank x4 = 4-bit x8 = 8-bit L = Low voltage (1.35v) U = Ultra low voltage (1.25v) Blank or omitted = Standard 12800 = 1600-MT/s 10600 = 1333-MT/s 8500 = 1066-MT/s R = RDIMM (registered) E = UDIMM (unbuffered with ECC) L = LRDIMM (load reduced) Hardware options installation 49

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Hardware options installation 49
Dual- and quad-rank DIMMs provide the greatest capacity with the existing memory technology. For
example, if current DRAM technology supports 8-GB single-rank DIMMs, a dual-rank DIMM would be 16
GB, and a quad-rank DIMM would be 32 GB.
LRDIMMs are labeled as quad-rank DIMMs; however, they function more like dual-rank DIMMs. There are
four ranks of DRAM on the DIMM, but the LRDIMM buffer creates an abstraction that allows the DIMM to
appear as a dual-rank DIMM to the system. The LRDIMM buffer also isolates the electrical loading of the
DRAM from the system to allow for faster operation. These two changes allow the system to support up to
three LRDIMMs per memory channel, providing for up to 50% greater memory capacity and higher memory
operating speed compared to quad-rank RDIMMs.
DIMM identification
To determine DIMM characteristics, use the label attached to the DIMM and the following illustration and
table.
Item
Description
Definition
1
Size
—
2
Rank
1R = Single-rank
2R = Dual-rank
4R = Quad-rank
3
Data width
x4 = 4-bit
x8 = 8-bit
4
Voltage rating
L = Low voltage (1.35v)
U = Ultra low voltage (1.25v)
Blank or omitted = Standard
5
Memory speed
12800 = 1600-MT/s
10600 = 1333-MT/s
8500 = 1066-MT/s
6
DIMM type
R = RDIMM (registered)
E = UDIMM (unbuffered with ECC)
L = LRDIMM (load reduced)