Hardware options installation  56 
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) 
 
For the latest supported memory information, see the QuickSpecs on the HP website 
(http://h18000.www1.hp.com/products/quickspecs/ProductBulletin.html). At the website, choose the 
geographic region, and then locate the product by name or product category.