For our tests we put together the following platform:
- CPU: Core i7-860 (Lynnfield, 4 cores/8 threads, 2.8 GHz, 8 MB L3);
- Mainboard: ASUS P7P55D Premium (LGA1156, Intel P55 Express);
- Memory: 2 x 2 GB, DDR3 SDRAM, Kingston KHX1866C9D3LK2/4GX;
- Graphics card: ATI Radeon HD 5870;
- HDD: Western Digital VelociRaptor WD3000HLFS;
- CPU cooler: Thermalright Ultra-120 eXtreme with Enermax Everest fan;
- PSU: Tagan TG880-U33II (880 W);
- OS: Microsoft Windows 7 Ultimate x64;
- Intel Chipset Driver 188.8.131.525;
- ATI Catalyst 10.5 Display Driver.
Power Consumption Tests
Since Kingston KHX1866C9D3LK2/4GX memory modules from the LoVo HypperX series we received for review are primarily targeted for energy-efficient systems, we decided to start with the power consumption tests that can show the real effect from using these “green” modules working at lower voltage.
However, before we start talking about the practical power consumption readings, we should say the following. It turned out that far not all desktop mainboards can actually set the DDR3 memory voltage below the standard 1.5 V. Today we are going to use an Asus platform so the minimal voltage on the DIMM slots was 1.2 V, but it seems to be more of an exception than a rule. Many mainboards, such as Gigabyte ones, for instance, can’t set such low voltages. At least not without the special BIOS modifications. So, if you really want to use energy-efficient memory from Kingston’s LoVo series, make sure that your mainboard has corresponding BIOS settings that would allow you to set the memory voltage lower than the nominal.
However, if it does allow you to set lower voltages, then you will immediately see the effect from the LoVo memory even without any measurements. The thing is that these memory modules barely heat during work. Therefore, the heat-spreaders obviously perform purely decorative aesthetic function, but have no practical value.
On the other hand, memory modules make minimal contribution to the power consumption of contemporary systems. Therefore, it would be too optimistic to expect low-voltage DDR3 SDRAM to have any serious influence on the total system power consumption.
You can see from the following graph how things are in reality. It shows total power consumption of our test system without the monitor when we install DDR3-1333 and DDR3-1600 SDRAM on Elpida “Hyper” chips with different voltages: lower 1.2-1.25 V, standard 1.5 V and higher 1.65 V, which is the setting used in all overclocker products. The power consumption was taken “past” the power supply unit and this value represents the total power consumption of all system components combined. In this case we do not take into account the efficiency of the PSU itself.
As we have expected, the influence from the memory is minimal. The power consumption difference between the system equipped with low-voltage and regular memory is only 2 W in idle mode and about 3 W under load. And it is no more than 5% of the entire platform power consumption.
In addition to the obtained results, we decided to compare the power consumption of an overclocked system with DDR3-1866 working at 1.35 V and at 1.65 V. These results are given separately, because you need to overclock the processor in order to have the memory work at this frequency. The CPU frequency was increased to 3.4 GHz (22 x 155 MHz). The peculiarity of this overclocking is that it doesn’t require any voltage increase for stable operation of the overclocked system. As a result, the system working in this mode can maintain an optimal ratio between its performance and power consumption.
The results are even less impressive than in the previous case. It is in fact quite logical, considering that you need 1.35 V of power in energy-efficient mode to ensure that the memory runs at 1866 MHz.
However, in defense of the low-voltage memory I have to say that its relative efficiency could have been more noticeable, if we had used energy-efficient and low-voltage component modifications, such as a mainboard with an integrated graphics core and an energy-efficient S-series processor. In other words, LoVo memory will come in very handy in an energy-efficient platform, but in common platforms it will hardly be justified, especially since it is about 10% more expensive than the regular memory modules.