HP BL2X220C - Manual (Page 23)

Hardware options installation 23
The memory subsystem in this server blade can support RDIMMs or UDIMMs. Both types are referred to as
DIMMs when the information applies to both types. When specified as RDIMM or UDIMM, the
information applies to that type only. All memory installed in the server blade must be the same type.
The server blade supports the following DIMM speeds:
• Single- and dual-rank PC3-10600 (DDR-1333) DIMMs operating at 1333 and 1066 MHz
• Quad-rank PC3-8500 (DDR-1067) DIMMs operating at 1066 MHz
Depending on the processor model, the number of DIMMs installed, and whether UDIMMs or RDIMMs
are installed, the memory clock speed may be reduced to 1066 or 800 MHz. For more information on
the effect of DIMM slot population, see "General DIMM slot population guidelines (on page 25 )."
Memory subsystem architecture
The memory subsystem in this server blade is divided into channels. Each processor supports three
channels, and each channel supports one DIMM slot, as shown in the following table.
Channel Slot Slot number
1 A 1
2 B 2
3 C 3
This multi-channel architecture provides enhanced performance in Advanced ECC mode. This server blade
supports either Registered PC3 DIMMs (RDIMMs) or Unbuffered DIMMs (UDIMMs).
DIMM slots in this server are identified by number and by letter. Letters identify the slots to populate. 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 blade 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.