Core i7-8086K 40th Anniversary CPU Review: Intel X86 Hits 5GHz

Intel Core i7-8086K: Overclocking And Power Consumption

We also spent some time overclocking the Core i7-8086K using the Gigabyte Z370 Gaming Ultra motherboard to see what kind of additional horsepower the processor had lurking under its hood. Because Coffee Lake has had some time to mature and Intel does some selective binning to ensure high clocks with these chips, we were interested to see how far we could push our sample.

Overclocking The Core i7-8086K
Pushing Coffee Lake Well Beyond Stock

Overclocking a Core i7-8086K processor is very similar to any other previous-gen Intel K-SKU processors, but like Skylake and Kaby Lake, Coffee Lake has one additional wrinkle. Because the processor is unlocked, overclocking it is simply a matter of altering a few multipliers, tweaking voltages, and dealing with the additional heat and power requirements. These processors can also be overclocked by adjusting BCLK frequencies though, so it's possible to really fine tune the end result.
Core i7-8086K Overclocked To 5.1GHz

We took a somewhat conservative approach to overclocking the Core i7-8086K, to give you all an approximate “worst case scenario”. Our results should be repeatable by most users, assuming you’ve got similar hardware and everything is working properly. You shouldn’t need exotic cooling to pull off what we did here. We used an off-the-shelf Corsair H80 AIO liquid cooler with the motherboard and processor installed in a mainstream NZXT mid-tower.

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Windows Booted At 5.2GHz, But The System Wasn't Fully Stable

To see what our sample could do, we manually cranked the core voltage up to 1.4v and shot for a modest 5GHz (50x100MHz) all core-boost, which worked without incident. We then moved up to 5.2GHz, but had some instability under load, so we bumped the voltage but couldn't get things completely stable with all-cores under load. We backed things down to 5.1GHz, however, and things stabilized, but we were flirting with the upper temperature limits with our setup. At 5.1GHz, the CPU was perfectly stable and operated in the upper 80-degree range when under load. Idle temperatures were relatively cool and stayed in the upper 30's (when not overclocked, temps peaked in the upper 60s with our setup).

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While we had the chip overclocked, we re-ran a few benchmarks and saw some decent performance improvements that were large enough to push the 6-core chip into the same territory as the 8-core Ryzen 7 2700X in these multi-threaded tests.

We should note, however, that our Core i7-8700K peaked at only 5GHz, so there appears to be some additional overclocking headroom available with the 8086K.

Total System Power Consumption
Tested at the Outlet

Throughout all of our benchmarking and testing, we also monitored how much power our Coffee Lake-based test system was consuming with a power meter, versus the other systems we used for benchmark comparisons.

Our goal was to give you an idea as to how much power each configuration used while idling at the Windows desktop and while under a heavy CPU workload. Keep in mind, this is total system power consumption being measured at the outlet and not the the individual power of the CPUs alone.


Despite its higher max turbo clock, the Core i7-8086K actually consumed slightly less power than the Core i7-8700K, under both idle and load conditions. The differences aren't huge, but hint at the binning Intel has done and maturity of the platform at this point.

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We also monitored power consumption while overclocked and saw a huge 100 watt increase under-load, due to the higher clocks and voltages used to hit 5.1GHz. The jump in power while overclocked was somewhat surprising, but when you push many cores with higher voltages and frequencies, there's always going to be some additional power (and heat) to contend with.

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