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Power Consumption

CPUs of the Core i3 class are often used in low-power computers. Being fast enough for many everyday applications, they don’t require much power and don’t dissipate much heat, so they are perfect for compact HTPCs, for example. The Haswell-based Core i3 products promise an unprecedented performance/watt ratio because, as we've seen in our tests, they have become faster but have a lower specified TDP. According to the official specs, their TDP is 54 watts, which is 1 watt lower than specified for the Ivy Bridge Core i3 CPUs.

The Haswell microarchitecture increased the power requirements of Intel’s quad-core CPUs, so we are curious to measure the power consumption of the entire Core i3 4000 series now. The graphs below (unless specified otherwise) show the full power draw of the computer (without the monitor) from the wall socket. It is the total power consumption of all system components. The PSU's efficiency is taken into account but our Corsair AX760i is a highly efficient 80 PLUS Platinum product, so its effect on the result is very small.

The CPUs are loaded by running the 64-bit version of LinX 0.6.4 utility with support for AVX and FMA instructions. Moreover, we enable Turbo mode and all power-saving technologies to correctly measure the computer's power draw in idle mode: C1E, C6, Enhanced Intel SpeedStep and AMD Cool’n’Quiet.

The Haswell microarchitecture is unrivalled among today’s CPU designs when it comes to the power consumption in idle mode. The diagram just proves this point once again. Intel has polished off its power-saving technologies very well.

It must be noted that the GeForce GTX 780 contributes a lot to the total power draw of our test configuration in idle mode. The Haswell would enjoy a larger advantage if we used the integrated graphics cores. The new Core i3 CPUs would require 30 to 35 watts in that case.

The Haswell-based CPUs are comparable to the Ivy Bridge generation in terms of power consumption at single-threaded loads. That’s good as their power draw remains at a rather low level. For example, AMD's CPUs need 40 to 45 watts more at such loads.

When running the resource-consuming Linx 0.6.4 AVX utility, the AMD CPUs call for a lot of power. Intel's modern products with comparable performance need only half as much. Although the Haswell-based Core i3 models are theoretically more economical than their dual-core predecessors, they actually consume a few watts more at maximum loads. So, their reduced TDP is not reflected in real-life applications. It is hard to explain why but you should be aware that desktop PCs with Ivy Bridge CPUs are generally a little more economical at peak loads than their Haswell-based counterparts.

The higher power requirements of the Haswell-based Core i3 products would become even more evident if we used the integrated graphics core instead of the discrete graphics card. When there’s high load on the x86 and graphics cores, the i3-4340 will require up to 110 watts whereas a comparable configuration with a dual-core Ivy Bridge, which has a GT2-class graphics core, needs no more than 90 watts. On the other hand, the new Core i3 CPUs are faster in terms of both x86 and graphics cores.

 
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