Articles: CPU

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Power Consumption

While Ivy Bridge microarchitecture doesn’t deliver any significant boost in the computational performance, it can provide other benefits. For example, it allows lowering power consumption and heat dissipation due to the core design as well as due to the transition to 22 nm production process and use of tri-gate transistors. When we tested Core i5 processor with Ivy Bridge microarchitecture, we pointed out that the power consumption of systems with them has dropped by about 10-15% compared with the power consumption of systems with Sandy Bridge based CPUs inside. We expect Core i3 processors to demonstrate about the same improvement of energy-efficiency, especially since the use of new microarchitecture allowed Intel to lower their TDP by 15%: from 65 to 55 W.

To get a better idea of how greatly the processor’ energy-efficiency actually improved we performed a round of special tests. The new digital power supply unit from Corsair – AX1200i – allows monitoring consumed and produced electrical power, which we use actively during our power consumption tests. The graphs below (unless specified otherwise) show the full power draw of the computer (without the monitor) measured after the power supply. It is the total power consumption of all the system components. The PSU's efficiency is not taken into account. The CPUs are loaded by running the 64-bit version of LinX 0.6.4-AVX utility. Moreover, we enabled Turbo mode and all power-saving technologies to correctly measure computer's power draw in idle mode: C1E, C6, Enhanced Intel SpeedStep and AMD Cool’n’Quiet.

It is hardly possible to reveal any noticeable changes in the energy-efficiency of the LGA 1155 platform in idle mode. The thing is that in idle mode all contemporary processors switch to special power-saving modes, in which their power consumption is as low as a few watts. In these conditions the power appetites of other system components and the efficiency of the voltage regulator circuitry on the mainboard prevent us from estimating pure processor power consumption adequately. A great illustration to this fact would be low power consumption of the AMD A8-3870K based system. It can be explained not by some specific features of the CPU, but merely by the fact that this Socket FM1 platform is based on a Gigabyte mainboard, which boasts a simple CPU voltage regulator circuitry, which is highly efficient under low operational loads.

In case of single-threaded load processors with different microarchitectures demonstrate dramatically different levels of power consumption. And here we have every right to state that Ivy Bridge microarchitecture is the most energy-efficient among all testing participants. Core i3 manufactured with 22 nm process do win the promised 8-10 W of power from their predecessors and demonstrate overwhelming advantage over the competitor’s offerings. However, let’s take a look what will happen under heavy multi-threaded load.

No doubt that Core i3 processors from the new 3000 series will make the most energy-efficient systems. Their power consumption and therefore heat dissipation are significantly lower than by all other platforms, and their advantages over the systems with dual-core Sandy Bridge processors is between 10 and 20 W. This makes Core i3 with Ivy Bridge microarchitecture a perfect choice for compact and energy-efficient systems. And, by the way, for these particular systems Intel has special energy-efficient Core i3 CPU modifications with 35 W TDP instead of 55 W.

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