DDR3 memory technology

when running at the same speed (800 MT/s). At 1333 MT/s, DDR3 uses about the same power as

DDR2 memory while providing an improvement in maximum bandwidth.

The new 1600 MT/s DDR3 RDIMMs for the ProLiant Gen8 servers use 1.5V and consume the most

power. Running at 1600 MT/s, DDR3-1600 memory uses about 15% more power than the equivalent

DDR3-1333 memory in G6 and G7 servers.

DDR3 also has two power savings modes that the memory controller can employ to reduce memory

power consumption further—CKE power down and self-refresh mode. With CKE power down, the

memory controller performs a look-ahead at the queue of pending memory operations. If none are

scheduled for a particular DIMM, then the controller places the DIMM in a lower power state and

only re-awakens it for refreshes. For additional power savings, the memory controller will place the

DRAMs in self-refresh mode whenever the system CPU enters a power down state (C6 for Intel

processors). When this occurs, the DIMM goes into a still lower power state and performs its own

refresh cycles.

Low-voltage DDR3 memory for ProLiant G6 and G7 servers

DDR3 memory is also available in low-voltage DIMMs, which operate at 1.35V instead of the 1.5V

for standard DDR3 DIMMs. Low-voltage DDR3 DIMMs consume 10 to 15% less power than standard

DDR3 DIMMs. A dual-rank 8 GB low-voltage DDR3 DIMM running at 1333 MT/s consumes about

8.5 watts compared to the 10 watts that a standard voltage DIMM consumes. At lower voltage,

electrical loading and signal integrity are greater challenges. For these reasons, low-voltage DDR3

DIMMs are available only in single- and dual-rank configurations.

The low-voltage DDR3 DIMMs for G6 and G7 servers cannot operate at full speed when the number

of DIMMs installed per channel increases. Tables 3 and 4 summarize low-voltage DDR3 DIMM

operation in G6 and G7 ProLiant servers.

Table 3: Operation of low-voltage DDR3 DIMMs in AMD-based ProLiant G7 servers

1 DIMM per channel 2 DIMMs per channel 3 DIMMs per channel

Single Rank

1333 MT/s @ 1.35V 1333 MT/s @ 1.35V 1066 MT/s @ 1.35V

Dual Rank 1333 MT/s @ 1.35V 1333 MT/s @ 1.35V 800 MT/s @ 1.35V

Table 4: Operation of low-voltage DDR3 DIMMs in Intel-based 2P ProLiant G6 servers

1 DIMM per channel 2 DIMMs per channel 3 DIMMs per channel

Single Rank

1333 MT/s @ 1.35V 1333 MT/s @ 1.35V

1066 MT/s @ 1.35V

(UDIMMs)

800 MT/s @ 1.35V

Dual Rank 1333 MT/s @ 1.35V 1066 MT/s @ 1.35V 800 MT/s @ 1.35V

As these tables illustrate, low-voltage DDR3 DIMMs for G6 and G7 servers reduce power

consumption, but they operate at lower data rates in larger configurations. In some cases, these

speeds are lower than the data rates at which standard voltage DIMMs operate.

HP SmartMemory for ProLiant Gen8 servers

HP SmartMemory DIMMs enable extended performance and manageability features on HP ProLiant

Gen8 servers. For the 2P ProLiant Gen8 servers using the Intel E5-2600 series of processors, HP