Overclocking, Power Consumption & Temperatures
Our overclocking efforts started at an easy 5 GHz. Pushing up to 5.2 GHz, Windows would boot and most games still ran. However, Cinebench crashed on us. Then LuxRender started having stability issues at 5.1 GHz. In the end, Creo 3.0, SolidWorks, and some of the HPC applications also cratered at 5 GHz. So, we dropped to a completely stable 4.9 GHz.
Surprisingly, the power consumption and performance curves are nearly superimposed, while the Core i7-8700K showed a flatter performance curve after 4.8 GHz. Without Hyper-Threading, the -8600K's memory bandwidth is obviously sufficient for perfect scaling (even if the absolute performance results are lower).
At idle, the differences in power consumption are fairly marginal. All of the processors end up just about where we'd expect based on previous reviews. AMD's Ryzen processors draw significantly more power than the Intel competition because their idle clock rate is a bit too high.
Chalk up the differences within 1W to a margin of error, even though we're measuring over a 30-minute period. The overclocked Core i5-8600K sees sporadic and unavoidable load peaks that mess with its average.
The new Intel CPU’s average power consumption in applications that combine 2D and 3D loads (like AutoCAD) is in line with the performance we observed.
Gaming paints a more balanced, but very similar picture.
The finishing order changes dramatically once we fire up an AVX stress test with all cores running at their top Turbo Boost bins. During rendering, we were seeing the -8600K's stock power consumption at 78W, climbing to 103W under a 5 GHz overclock.
AVX without offset pushes the result as high as 163W. The Core i5-8600K at 4.9 GHz even throttles due to its package temperature. And that's in spite of our compressor cooler's efforts! Thermal paste under the IHS does us no favors.
Here’s the good news: unless you render or run Prime95 for hours on end, a good air cooler can theoretically handle 4.9 GHz in a well-ventilated case. Intel’s thermal interface material isn't desirable, but it shouldn't stop you from achieving a decent overclock.
The above graph shows that a closed-loop liquid cooler is able to keep an overclocked Core i5-8600K from throttling after 20 minutes of warming up. A good heat sink and fan combination should perform almost as well, again, given ample airflow.
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