HP ProLiant SL250s Gen8 Server - Manual (Page 39)

Hardware options installation 39
HP SmartMemory
HP SmartMemory, introduced for Gen8 servers, authenticates and unlocks certain features available only on
HP Qualified memory and verifies whether installed memory has passed HP qualification and test processes.
Qualified memory is performance-tuned for HP ProLiant and BladeSystem servers and provides future
enhanced support through HP Active Health and manageability software.
Certain performance features are unique with HP SmartMemory. HP SmartMemory 1.35V DDR3-1333
Registered memory is engineered to achieve the same performance level as 1.5V memory. For example,
while the industry supports DDR3-1333 RDIMM at 1.5V, this Gen8 server supports DDR3-1333 RDIMM at
1.35V. This difference equates to up to 20% less power at the DIMM level with no performance penalty.
Memory subsystem architecture
The memory subsystem in this server is divided into channels. Each processor supports four channels, and
each channel supports two DIMM slots, as shown in the following table.
Channel Slot Slot number
1 A
E 1
2
2 B
F
3
4
3 C
G
8
7
4 D
H
6
5
For the location of the slot numbers, see "DIMM slot locations (on page 10 )."
This multi-channel architecture provides enhanced performance in Advanced ECC mode. This architecture
also enables the Lockstep memory mode.
DIMM slots in this server are identified by number and by letter. Letters identify the population order. Slot
numbers indicate the DIMM slot ID for spare replacement.
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.