HP ProLiant DL360e Configuring and using DDR3 memory with HP ProLiant Gen8 Ser - Page 19

Mixing DIMM sizes, General guidelines, Optimizing for lowest power consumption - gen8 power consumption

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Table 13: Lower system power consumption with three 8 GB LV RDIMMs per channel at 1.35V vs. 1.5V operation in a 24 slot HP ProLiant Gen8 server Throughput (GB/s) Idle Power (W) Loaded Power (W) 3 DPC @ 1.5V 60.5 16.6 98.6 3DPC @ 1.35V 60.5 15.5 78.8 Delta 0% 7% lower 20% lower HP 1333 MT/s SmartMemory LRDIMMs are capable of operating at 1.35V at one and two DIMMs per channel and 1066 MT/s at three DIMMs per channel. Standard RDIMMs require 1.5V operation to maintain 1333 MT/s speed at one and two DIMMs per channel. As Table 14 shows, using HP SmartMemory saves about 20% on power consumption while providing the same performance as standard DIMMs in 2 DIMM per channel configurations Table 14: Lower power consumption with two 32 GB LRDIMMs per channel at 1.35V vs. 1.5V operation 2 DPC @ 1.5V 2DPC @ 1.35V Delta Throughput (GB/s) 68.07 68.11 0% Idle Power 38.4 35.32 9% lower Loaded Power (W) 139.40 110.8 20% lower Mixing DIMM sizes There are no performance implications for mixing sets of different capacity DIMMs at the same operating speed. For example, latency and throughput will not be negatively impacted by installing 8 x 4GB singlerank DDR3-1333 DIMMs (one per channel), plus 8 x 8GB dual-rank DDR3-1333 DIMMs (one per channel). General guidelines For optimal throughput and latency, populate all four channels of each installed CPU identically. Optimizing for lowest power consumption The power that a DIMM consumes in a system is determined by several factors. These include the DIMM technology used as well as the DIMM's capacity, the number of ranks, and the operating speed. Let's take a quick look at each of these to see how they affect power consumption. DIMM types and power consumption Because they do not use any buffering, UDIMMs are the lowest power consuming DIMM type. As Figure 10 shows, 4GB UDIMMs consume about 35% less power than the comparable RDIMM. In general larger capacity DIMMs, which are powering multiple ranks of DRAMs, consume more power. However, on a per gigabyte basis they are more efficient. A 32GB LRDIMM consumes 9 watts under load, but this is about one-half the power per GB of an 8 GB RDIMM. 19

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Table 13:
Lower system power consumption with three 8 GB LV RDIMMs per channel at 1.35V vs. 1.5V operation in a
24 slot HP ProLiant Gen8 server
3 DPC @ 1.5V
3DPC @ 1.35V
Delta
Throughput (GB/s)
60.5
60.5
0%
Idle Power (W)
16.6
15.5
7% lower
Loaded Power (W)
98.6
78.8
20% lower
HP 1333 MT/s SmartMemory LRDIMMs are capable of operating at 1.35V at one and two DIMMs per
channel and 1066 MT/s at three DIMMs per channel. Standard RDIMMs require 1.5V operation to
maintain 1333 MT/s speed at one and two DIMMs per channel. As Table 14 shows, using HP
SmartMemory saves about 20% on power consumption while providing the same performance as standard
DIMMs in 2 DIMM per channel configurations
Table 14:
Lower power consumption with two 32 GB LRDIMMs per channel at 1.35V vs. 1.5V operation
2 DPC @ 1.5V
2DPC @ 1.35V
Delta
Throughput (GB/s)
68.07
68.11
0%
Idle Power
38.4
35.32
9% lower
Loaded Power (W)
139.40
110.8
20%
lower
Mixing DIMM sizes
There are no performance implications for mixing sets of different capacity DIMMs at the same operating
speed. For example, latency and throughput will not be negatively impacted by installing 8 x 4GB single-
rank DDR3-1333 DIMMs (one per channel), plus 8 x 8GB dual-rank DDR3-1333 DIMMs (one per
channel).
General guidelines
For optimal throughput and latency, populate all four channels of each installed CPU identically.
Optimizing for lowest power consumption
The power that a DIMM consumes in a system is determined by several factors. These include the DIMM
technology used as well as the DIMM’s capacity, the number of ranks, and the operating speed. Let’s take
a quick look at each of these to see how they affect power consumption.
DIMM types and power consumption
Because they do not use any buffering, UDIMMs are the lowest power consuming DIMM type. As Figure
10 shows, 4GB UDIMMs consume about 35% less power than the comparable RDIMM. In general larger
capacity DIMMs, which are powering multiple ranks of DRAMs, consume more power. However, on a per
gigabyte basis they are more efficient. A 32GB LRDIMM consumes 9 watts under load, but this is about
one-half the power per GB of an 8 GB RDIMM.