User guide

Hardware options installation 42
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.
Memory configurations
To optimize server availability, the server supports the following AMP modes:
• Advanced ECC—provides the greatest memory capacity for a given DIMM size, while providing up to
4-bit error correction. This mode is the default option for this server.
• Mirrored Memory—provides maximum protection against failed DIMMs. Uncorrectable errors in one
channel are corrected by the mirror channel.
• Lockstep—provides enhanced protection while making all installed memory available to the operating
system. The server can continue to function if a single- or multi-bit memory failure within a single DRAM
device occurs.
Advanced Memory Protection options are configured in RBSU. If the requested AMP mode is not supported
by the installed DIMM configuration, the server boots in Advanced ECC mode. For more information, see
"HP ROM-Based Setup Utility (on page 86)."
For the latest memory configuration information, see the QuickSpecs on the HP website
(http://www.hp.com).
RDIMM maximum memory configurations
The following table lists the maximum memory configuration possible with 8-GB RDIMMs.
Rank Processor
Single-rank
72 GB
Dual-rank
72 GB
Quad-rank
48 GB
UDIMM maximum memory configurations
The server supports a maximum of 24 GB using 4-GB dual-rank UDIMMs.
Low voltage DIMMs
Low Voltage DDR3 DIMMs operate at a lower voltage (1.35V) than standard voltage DDR3 DIMMs (1.5V),
and therefore consume less power. However, LVDIMMs are configured to operated at standard voltage
levels (1.5V) under the following conditions:
• If LVDIMMs are mixed with standard DDR3 DIMMs on the same server, the LVDIMMs operate at 1.5V.
• If there are two dual-rank LVDIMMs per channel on any populated memory channel in the system
running at 1333 MHz, the LVDIMMs operate at 1.5V.
This setting preserves maximum memory subsystem performance. To have DIMMs operate at 1.35V,
configure the Maximum Memory Bus Frequency option in the ROM-Based Setup Utility to 1066 MHz.