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Intel's Core i7-8700K CPU reviewed


Six shots of Coffee Lake, please
— 8:01 AM on October 5, 2017

How quickly things change. Just nine months ago, Intel introduced the Core i7-7700K, its seventh in a line of four-core, eight-thread enthusiast processors that stretches back to 2010. We contented ourselves with about a 5% performance increase on average from that chip compared to the Core i7-6700K before it. A proven formula got a little bit better, and that was that.

Shortly after that quiet bit of incremental progress, AMD upended the status quo like an errant speck of dust in a 193-nm stepper with its Zen architecture and Ryzen CPUs. Builders could suddenly get more cores and threads for their dollar than ever before. Every one of those chips was overclockable, and they didn't suffer from nipping and tucking to satisfy product-segmentation whims. Most importantly, AMD spoke directly to the hearts and minds of the brightest spot of today's PC market: enthusiasts and gamers. Nobody less than CEO Lisa Su talked up the company's focus on high-performance products for that audience, and AMD backed up that talk with a full range of desktop chips spanning prices from about $100 to $1000 and everywhere in between.

In the face of this onslaught, the i7-7700K easily maintained its dominance in single-threaded performance and high-refresh-rate gaming, but it was suddenly matched in just about every other measure of performance by chips selling for about $100 less. Whatever Intel's plans may have been at that time, it was clear that the four-core, eight-thread formula wasn't going to be enough to hold the line any longer for mainstream PCs.


The Core i7-8700K

That brings us to Intel's eighth generation of Core desktop processors, code-named Coffee Lake, that launch this morning. These CPUs don't combat the Ryzen threat with a major microarchitecture change or even a process shrink. Instead, the company has continued to improve its 14-nm process for another generation of CPUs powered by the Skylake microarchitecture. Although the exact nature of those improvements is classified, they are at least partially responsible for letting the company put more cores in its mainstream CPUs at every price bracket, and those higher core counts are how Intel hopes to extract the performance leap that the eighth-generation Core name suggests.

Make no mistake: this is a major change for Intel's entire product stack. Coffee Lake Core i7s ditch the four-core, eight-thread configuration that's been the top-end Core i7 formula for the better part of a decade. Instead, those chips now have six cores and 12 threads at their disposal. Core i5 chips now have six cores and six threads, and Core i3s have gone from dual-core designs with Hyper-Threading to native four-core parts without. Given Intel's clock-speed and architectural advantages over today's Ryzen CPUs, this full-court press seems poised to slow AMD's momentum in regaining desktop CPU market share.


The six-core Coffee Lake-S die. Source: Intel

Outside of those very high-level changes, however Intel is basically treating these chips as black boxes, aside from the fancy die shot you see above. Die size, transistor count, and the exact nature of the process improvements Intel has been able to extract from its 14-nm fabs remain mysteries.

We do know that the 14nm++ process, as it's called, can handle a 23% to 24% higher drive current (a measure directly associated with how fast a transistor can operate) with only minor increases in leakage current, at worst, thanks to a mantra of constant improvement over the life cycle of a given process node. The company disclosed as much at its Technology and Manufacturing Day earlier this year.

In total, the company claims the improvements in 14nm++ can allow for transistor performance increases of up to 26% at the same power level compared to the process' status in 2015. Perhaps more astoundingly, the company can get the same level of performance on 14nm++ as one of its 2015 transistors for 52% less power. These developments are most likely a large part of what allowed the company to perform feats like putting four cores in a 15W TDP and six cores in a 95W TDP.

Outside of what it's presented in its manufacturing day events, however, we don't have any specific inkling of how those process improvements are put to use in Coffee Lake. In the finest tradition of Andy Grove, the company now seems unwilling to let even the slightest hint of competitively useful information slip its clean-room walls. Given AMD's resurgence, this paranoia is perhaps justifiable. Tipping off your competitors about how, exactly, your fabs are improving is perhaps not the wisest course of action.

Just like the birds and the bees in the age of the Internet, however, curious folk can find enough things out on their own to be dangerous. Someone will certainly figure out the die size of Coffee Lake-S by simply popping the IHS off a chip and using some calipers—not exactly nation-state levels of industrial espionage. Transistor count and process improvements can't be gauged nearly as easily, but firms like TechInsights will surely take a guess (or probably better, for those willing and able to pay). So long as that's all that happens, however, Intel seems to be happy to let the rumors swirl.

This secrecy is kind of a shame, because the company's process technology at 14 nanometers is clearly one of its greater competitive advantages. It'd be neat to hear what has allowed the company to boost the performance of its transistors quite so much on the same node, but in such a cutthroat industry as fabrication, Intel has no reason to tip its hand to competitors. For now, though, let's examine the implementations of Coffee Lake that are launching today.