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Power Consumption

The small performance benefits of the new-generation CPUs might be expected but what about their energy efficiency?

There were rumors that Intel increased the TDP of the senior 22nm CPUs to 95 watts although had planned to set it at 77 watts. Intel representatives told us that it was just a rumor, though. The actual TDP of the new CPUs, including the Core i7-3770K, is indeed limited to 77 watts but 95 watts is written on their packaging in order to maintain the standard scale of 35/65/95 watts that many Intel partners have got used to. Thus, the Ivy Bridge series can be expected to consume about 20% less power compared to the 95-watt CPUs with the previous microarchitecture.

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 of the 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 and Enhanced Intel SpeedStep.

When idle, the Ivy Bridge systems consume about the same amount of power as the Sandy Bridge counterparts because the EIST technology sets their voltage at 0.9 volts, similar to the minimum voltage of Sandy Bridge CPUs. As a matter of fact, modern CPUs account for but a small share of the total power consumption of a computer when idle.

The benefits of the 22nm tech process and tri-gate transistors become apparent at full load. The Core i7-3770K consumes 20% less than the Core i7-2700K, while the difference between the Core i5-3570K and Core i5-2500K configurations amounts to 13%. Moreover, the senior quad-core Ivy Bridge is more economical than the Core i5-2500K! So, the new CPUs are indeed superior in energy efficiency. And we haven’t yet seen Ivy Bridge CPUs with reduced TDP!

Testing power consumption at single-threaded load is interesting because modern CPUs enable turbo mode in this case, delivering higher performance while keeping the power consumption and heat dissipation within reasonable limits. The Core i7 3770K and Core i5-3570K turn out to be more economical than the Sandy Bridge in this test as well.

Thus, the Ivy Bridge series has no rivals in terms of performance per watt. And this seems to be its key advantage considering its overclocking potential which we’ll discuss below.

 
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