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Power Consumption

The performance benefits provided by the Haswell Refresh series do not impress us. Still, they might be better than their predecessors in terms of thermal or electrical properties due to improvements in their manufacturing technology. Let’s check this out.

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. We enable Turbo technology and all power-saving technologies: C1E, C6 and Enhanced Intel SpeedStep.

First we test our PC configurations in idle mode.

All of the processors have the same results here. The Haswell switches into a power-saving state when idle, minimizing its power consumption to zero. So the numbers in the diagram are rather indicative of the power draw of the rest of the configuration.

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.

The diagram makes it clear that the Haswell Refresh processors are no improvement in terms of power consumption. The new and faster models need more power than their predecessors. The 100MHz increase in clock rate results in a 5% increase in power consumption. Despite this fact, Intel doesn't change the TDP, so the heat dissipation of any Core i7 and i5 must be within 84 watts. The Core i3 series is supposed to consume no more than 54 watts.

The Linpack-based LinX utility makes the processor consume much more power than at average real-life loads, so we will have a more realistic test as well. We will transcode a video clip using the 64-bit x264 codec version r2431.

The overall picture is the same as in the LinX test but the numbers are lower. Anyway, the Haswell Refresh processors consume 5% more than their predecessors. There seem to be no improvements in terms of power consumption.

As for temperature, the Haswell Refresh processors have the same low-efficiency thermal interface as before. Their temperature rises sharply as soon as you launch a heavy application and remains high even if you've got an efficient CPU cooler. In our case, with the Noctua NH-U14S cooler, the senior Haswell Refresh model, Core i7-4790, quickly got as hot as 84°C while running LinX - without any overclocking on our part!

We can remind you that Haswell-based processors enable thermal throttling at 100°C.

Conclusion

The Haswell Refresh brand covers ordinary enough processors that don’t have anything new to offer to the public. Intel didn't do any engineering work with them, so the consumer properties of the new LGA1150 CPUs are the same as before including the number of x86 cores, the amount of cache memory, the type of the integrated graphics core, and the supported technologies. There are no optimizations in the semiconductor die, so the Haswell Refresh is identical to the Haswell in terms of power consumption and heat dissipation, too.

The only real improvement is about the clock rate but it is only achieved by overclocking old processors. It is increased by 100 MHz only, so the performance benefits are very small. The new Haswell Refresh processors are a mere 2-3% faster than their Haswell predecessors in our tests.

Thus, Haswell Refresh CPUs may only be interesting for users who buy their first LGA1150 computer. The new CPUs come at the same prices as the old ones, so it makes sense to prefer them and get slightly higher performance for the same money.

Moreover, two more Haswell Refresh products are going to be revealed in the next few weeks. These are the overclocker-friendly Core i7-4790K and Core i5-4690K. Codenamed Devil’s Canyon, they will feature much higher clock rates, lower operating temperature and better overclocking potential. We will test them as soon as they come out.

 
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