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Intel's Core i7-7700K 'Kaby Lake' CPU reviewed


Heavy lies the crown
— 11:00 AM on January 3, 2017

It's tough to be at the top of your game. The Tiger Woodses, Roger Federers, and Lebron Jameses of the world can blaze all the paths they want, set all the records, break all the barriers, force the invention of new metaphors for pushing the bounds of what's possible. They win and win and win some more. Eventually, though, even the best and brightest have to stumble—or, at least, plateau.

About six years ago to this day, Intel launched the brilliant Sandy Bridge family of CPUs to universal acclaim. Clock for clock, Sandy Bridge redefined desktop performance by every measure we cared to test. Folks building new PCs in 2011 had ample reason to retire even their Nehalem and Lynnfield PCs in favor of Sandy Bridge. Overclockers enjoyed plenty of "free" headroom from K-series Sandy CPUs with modest aftermarket coolers on top. Life was very, very good.

Intel followed Sandy Bridge with Ivy Bridge, the process-advance "tick" to Sandy's architectural "tock." While Ivy delivered some under-the-hood improvements to Sandy's microarchitecture and its instructions-per-clock throughput, the big changes on the third-generation Core chips came in the integrated-graphics and power-efficiency departments as Intel began chasing thin-and-light notebooks with vigor.

Enthusiasts with Sandy Bridge CPUs still ended up sitting pretty when Ivy came around. Intel's third-generation Core chips proved less-forgiving overclockers than their forebears, and their performance improvements on the desktop weren't overwhelming compared to Sandy.

Meanwhile, AMD's ambitious Bulldozer architecture failed to demolish Sandy Bridge Core i5s, much less the Core i7-2600K. Even with AMD's subsequent refinements, Bulldozer's derivatives never quite matched the killer combo of single-threaded performance, power efficiency, and gaming competence that Intel delivered with tick-tock regularity. The potent Radeon integrated graphics in AMD APUs did little to capture the enthusiast imagination, either.

As Intel continued to perfect its microarchitectures and fabrication processes, the Haswell, Broadwell, and Skylake architectures each brought progressively more modest single-threaded performance improvements with them. The Skylake Core i7-6700K, Intel's most recent mainstream desktop range-topper, is one of the finest all-around CPUs ever made, and its only peers come from past generations of Core i7s.

With that long line of winners, AMD's perennial struggles with its CPUs and APUs, and the maddeningly difficult pursuit of smaller process technologies industry-wide, Intel's processors have enjoyed more-or-less complete domination of the PC in recent years. How many among us can say they have nothing left to beat but their own past successes? Indeed, when you're doing so well, what's the motivation to stick your neck out even further and perhaps overplay your hand?


The quad-core Kaby Lake die. Source: Intel

And that brings us to this morning. Even in light of the slowing pace of per-clock performance improvements from Intel, the Core i7-7700K CPU that's launching today feels like the company's least-ambitious desktop chip in quite some time. From dispatch to retirement, the i7-7700K's basic Kaby Lake CPU core is identical to Skylake's. Aside from some improvements in its fixed-function video engines to efficiently handle 4K video encoded with the next-gen HEVC and VP9 video codecs, Kaby's integrated graphics are largely a carry-over from the Gen9 IGP technology on Skylake chips, too. Womp.


The Skylake Core i5-6600K (left) and the Kaby Lake Core i7-7700K (right)

Basically every item on our wish list for Kaby was dashed during Intel's Kaby Lake introduction earlier this year at IDF. No, there will be no eDRAM for socketed Kaby Lake CPUs. No, VESA Adaptive-Sync still hasn't been integrated into the Kaby Lake IGP. So on and so forth. If you were hoping for some revolutionary architectural change from Intel to mark the seventh generation of Core processors and put the last nail in Sandy Bridge's coffin, well, Kaby Lake ain't it.


i5-6600K on the left, i7-7700K on the right

Instead, the biggest change in Kaby comes when it's forged in Intel's foundries. Kaby is the first CPU from Intel's new "optimize" product phase, and that means the company has tweaked and tuned its 14-nm tri-gate transistors to extract every bit of performance possible from its fabs. With those improvements, the Core i7-7700K enjoys a 200-MHz base clock boost over the i7-6700K, to 4.2 GHz, and its Turbo clock is a dizzying 4.5 GHz. The Core i7-7700K's TDP has held steady at 91W even with that clock boost, halting a slow upward creep that began with Ivy Bridge. If there's any single-threaded performance improvement from Kaby, it should come entirely from this extra clock speed.

Like the Skylake CPUs before it, the Core i7-7700K also exposes a couple new knobs for overclockers to play with. Kaby Lake incorporates a new base-clock-aware dynamic-voltage-and-frequency-scaling (DVFS) feature that lets the CPU's power-management circuitry take both changes in the base clock and changes in multipliers into account when it adjusts the CPU's P-states. In the past, the company says that its CPUs' power-management circuitry only took multiplier changes into account in that scenario, so BCLK overclocking required finding a stable fixed voltage. The company says this new BCLK-aware approach lets overclockers enjoy a simpler BCLK tweaking process and the power-saving benefits of DVFS at idle.

Unlocked Kaby Lake chips also inherit Broadwell-E's AVX Offset feature. That setting lets tweakers run the chip at lower speeds under heavy AVX2 workloads while maintaining higher frequencies when those instructions aren't being executed, possibly increasing the light-load frequency gains one can achieve with a given chip. If those issues held you back from taking your Skylake CPU to its maximum potential, Kaby Lake might break those shackles.