Memory; Ddr-3; Dimm Choices - HP ProLiant DL160se - G6 Server Introduction Manual

Memory

Xeon 3400 and 5500 Series processors connect directly to memory rather than through a chipset.
They support only DDR-3 dual inline memory modules (DIMMs). In the ProLiant 100-series G6 servers,
HP manages all processor functionality options, including memory mirroring and memory channel
interleaving, through the G6 server BIOS and BIOS Setup Utility (BSU).

DDR-3

DDR-3 has several key enhancements including an 8-bit prefetch buffer for storing data before it is
requested. By comparison, DDR-2 has a 4-bit buffer. For DDR-3, the data signal rate can increase to
1333 Megatransfers per second (MT/s). While this is commonly referred to as having a speed of
1333 MHz, the maximum clock speed for the DIMMs is actually 667 MHz and the signal is double-
pumped to achieve the data rate of 1333 MT/s. DDR3-1333 DIMMs can operate at clock speeds of
667 MHz, 533 MHz, and 400 MHz with corresponding data rates of 1333, 1066, and 800 MT/s.
The three memory channels between each processor's integrated memory controller and its dedicated
DDR-3 memory provide a total bandwidth of 32 gigabytes per second.
HP DDR-3 DIMM modules incorporate an integrated thermal sensor that signals the chipset to throttle
memory traffic to the DIMM if its temperature exceeds a programmable critical trip point. Using the
data from these thermal sensors, ProLiant G6 servers can reduce fan speed when memory is idle,
which reduces power consumption. The BIOS in ProLiant G6 servers verifies the presence of the
thermal DIMM sensor during POST. Some third-party DIMMs may not include this thermal sensor. If it
is absent, a POST message will warn that the DIMM does not have a thermal sensor, and the fans will
be forced to run at higher speeds (requiring more power).

DIMM Choices

DDR-3 is available as both Unbuffered Dual In-line Memory Modules (UDIMMs) and Registered
(buffered) Dual In-line Memory Modules (RDIMMs). Both RDIMMs and UDIMMs support error
correcting code (ECC).
There are three types of DDR-3 available for ProLiant G6 servers:
• PC3-8500R (RDIMM, ECC compliant) —1066 or 800 MT/s data rate, depending on memory
configuration and processor installed.
• PC3-10600E (UDIMM, ECC compliant) —1333, 1066, or 800 MT/s data rate, depending on
memory configuration and processor installed.
• PC3-10600R (RDIMM, ECC compliant) —1333, 1066, or 800 MT/s data rate, depending on
memory configuration and processor installed.
Administrators can configure ProLiant 100-series G6 servers using either RDIMMs or UDIMMs but
RDIMM and UDIMM memory cannot be mixed within a single server
have up to 18 DIMM slots, allowing larger memory capacities than with platforms that used DDR-2.
ProLiant G6 servers optimize memory performance by operating DDR-3 memory at the maximum rate
possible based on the memory configuration and the processor that is installed.
When choosing memory configurations for ProLiant 100-series G6 systems, the following guidelines
should prove helpful:
• UDIMM configurations are limited to a maximum of two UDIMMs per memory channel because the
memory controller must drive the address and command signals to each DRAM chip on a channel.
This results in a 24 GB maximum configuration in ProLiant 100-series G6 servers. Because they
require fewer components, UDIMMs are typically less expensive than RDIMMs.
The ProLiant ML110 G6 server does not support RDIMM memory, only the PC3-10600E UDIMM
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2 . ProLiant 100-series G6 servers
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