Compared to their Ivy Bridge-E predecessors, the Haswell-E series feature a redesigned microarchitecture and more x86 cores (in the senior model), so it is quite surprising that their TDP hasn’t changed much. Of course, Intel had to reduce the clock rate of the 8-core i7-5960X Extreme Edition so that its power consumption wouldn’t be much higher compared to its 6-core predecessors. Anyway, we had some doubts that eight Haswell cores would be able to fit into the 140-watt TDP. We had to check this out in practice.
So, the graphs below 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 AX1200i is a highly efficient 80 PLUS Platinum product, so its effect on the result is very small. We enable Turbo technology and all power-saving technologies: C1E, C6 and Enhanced Intel SpeedStep.
The new LGA2011-v3 platform doesn’t offer any power-related benefits in idle mode. It needs about as much power as the older LGA2011 and more than the mainstream LGA1150 platform. It is no wonder because the Haswell-E design and the X99 chipset feature sophisticated integrated controllers. Moreover, the new CPUs do not support the C7 power-saving state.
When transcoding video with the x264 coder, the Core i7-5960X and Core i7-5930K are comparable in their power requirements. The Core i7-5820K is somewhat more economical, but any of the Haswell-E models needs more power than the Core i7-4960X. The higher specified TDPs of the new CPUs indeed reflect their increased power consumption, so the entire LGA2011-v3 platform is not only faster but also less economical. And the difference may be as large as 30 watts at high loads.
Next we measure the peak power consumption when our configurations run the 64-bit version of the LinX 0.6.5 utility (based on the Linpack suite) with support for the AVX2 instruction set.
We’ve got the same standings as in the previous test except that each CPU needs more power when running LinX. The Haswell-E have higher power requirements than their predecessors, both the 8- and 6-core models. We should also note that even modest overclocking provokes a serious increase in the power draw of the Haswell-E CPUs – by up to 200 watts in our tests. So if you’re planning to overclock your LGA2011-v3 platform, you should pay special attention to choosing an appropriate PSU and cooling system.