Besides its low-profile form-factor, Crucial’s Ballistix modules we’re testing today comply with the DDR3L standard and can work at a reduced voltage of only 1.35 volts. The reduced voltage means reduced power consumption, such memory being especially appropriate for mobile devices or servers. But since Crucial offers its DDR3L SDRAM to enthusiasts, we want to find out the benefits it can bring to desktop users.
First of all, you should be aware that DDR3L must be supported by the mainboard for the memory to work at 1.35 volts. Most mainboards from leading brands available today support DIMM voltages below 1.5 volts, yet you may want to make sure beforehand that your mainboard allows setting 1.35 volts as memory voltage in its BIOS. Our mainboard ASUS P8Z77-V Deluxe supports not only DDR3L but also DDR3U, letting us choose any voltage we like from 1.2 volts and higher with a step of only 0.005 volts.
So we can check out how much power our computer consumes if it has DDR3-1600 working at the standard voltage or 1.35 volts or at overclocked settings with a voltage of 1.65 volts. We use Crucial Ballistix Tactical LP DDR3-1600 2x8GB (BLT2K8G3D1608ET3LX0) for this test.
Our Corsair AX760i power supply supports power consumption monitoring and we use this capability for our tests. In the diagrams below, the computer’s full power draw (without the monitor) is shown as measured at the PSU’s output. It is the sum of each component’s power consumption while the PSU’s efficiency is not taken into account. The computer was running LinX 0.6.4 64-bit with AVX support using the full amount of system memory. To correctly measure the power consumption in idle mode, we enabled all power-saving technologies: C1E, C6 and Enhanced Intel SpeedStep.
When the computer is idle, DDR3L doesn’t provide any benefits compared to ordinary system memory. The DDR3 SDRAM modules do not contribute much to the overall power consumption. So, changing the memory voltage from 1.35 to 1.5 volts doesn’t produce any visible effect. Overclocking affects the overall power consumption, though. Working at 2200 MHz and 1.65 volts, the memory increases the computer’s power draw by 2 watts. On the other hand, it is possible that it is not the memory modules but the CPU-integrated DDR3 SDRAM controller that consumes more power as it has to work with the memory bus at a higher clock rate.
When there’s a high load on the computer, the picture doesn’t change much. The energy-efficient memory doesn’t affect the overall power consumption, especially if there’s an overclocked CPU inside. Compared to ordinary DDR3, DDR3L can save you a mere 2 watts. Overclocking the system memory increases the overall power draw by only 1.5%. Thus, the low voltage of the low-profile Crucial Ballistix modules can hardly be a serious advantage, at least if we’re talking about a typical overclocked computer with an Ivy Bridge processor and a dual-channel memory kit: DDR3L is roughly as economical as ordinary DDR3 SDRAM in this case.