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Intel Core i7-7700K review: Kaby Lake debuts for desktop

Intel's new Kaby Lake CPU hits the market today, but is it a worthwhile upgrade? How much performance did Intel's improved 14nm process yield? We review the core, explore these questions, and discuss our findings.
By Joel Hruska
KabyLakeDie

Today, Intel is taking the lid off its 7th Generation Core microprocessor family, codenamed Kaby Lake. It's been roughly five years since Intel last delivered a significant performance leap in a single generation and the Core i7-7700K has a number of challenges riding on its shoulders. This is the first new big-core processor since Intel switched from Tick-Tock, which alternated new process nodes with new architectures, to a three-step Process-Architecture-Optimization strategy. This is the second iteration of the Skylake core, but it's implemented on an advanced 14nm node, as Intel disclosed earlier this year. It's also the first Intel processor to support new Optane SSDs, provided the appropriate chipset is used (more on that later).

The Core i7-7700K also has the distinction of being the last chip generation Intel will launch before AMD's own Ryzen (née Zen) architecture debuts later this quarter, and you can bet AMD will be watching these results very closely when it comes to calibrating the speeds and feeds of their own CPU core. Put it all together, and this CPU launch is going to matter more than most. Let's take a look at what we've got to talk about -- first the platform, followed by the CPU and its performance.

The Z270 chipset

The Core i7-7700K and Core i7-6700K are both backwards and forwards-compatible, meaning you can drop a 6th-generation core into a new Z270 motherboard or pair a 7th-generation chip with the older Z170. We've covered the major differences below.

Z270-Diagram DRAM frequency: While we've had no problem using DDR4-3200 for our tests today, Z170's official support tops out at 2133MHz, compared with 2400MHz for Z270. Additional PCIe southbridge lanes: The Z170 supports 20 PCIe 3.0 lanes off the southbridge, Z270 offers 24. Intel Smart Connect: Intel Smart Connect periodically wakes your PC to download email or receive periodic push updates. This technology used to be offered on certain Intel desktop chipsets, but was removed after the Z87 debuted. The Z270 adds it as an optional feature.

There are a few new capabilities that require both a Z270 motherboard and a 7th generation CPU.

4K content streaming: 4K streaming is limited to Z270 boards and Kaby Lake CPUs, either because Intel only implemented full support for Microsoft's PlayReady 3.0 in its latest chips, or because only the 7th generation family supports hardware accelerated decode for 10-bit HEVC. 4K playback also requires at least the Anniversary Update of Windows 10 and is currently only available via Microsoft Edge. Intel Optane memory support: According to Intel, Optane will be available both as main memory and as the storage medium of choice for SSDs. The company has not clarified what interface its SSD drives will use, or if it intends to offer SATA, PCI-Express cards, or M.2-compatible chips. Optane memory (which means DIMMs) will only be available for Z270 chipsets, while Optane SSDs should be compatible with other platforms that support whatever standard Intel decides to ship. One notable missing feature? USB 3.1 Gen 2 support. Gen 2 offers transfer speeds of up to 10Gb/s, but Intel hasn't built a native controller capable of operating at these clock speeds. Some vendors may include support for this option, either by integrating third-party controllers or by using Intel's Alpine Ridge Thunderbolt 3 solution, which also offers USB 3.1 Gen 2 support.

The 7th-Gen Core i7 family

Intel is launching a number of Core i3, i5, and i7 desktop CPUs today, but the cores themselves are only modestly different than what we saw with Skylake back in 2015. As we've previously discussed, Kaby Lake is built on a new second-generation 14nm process node with a predicted 12% performance increase. H.265 Main10 and VP9 8-bit and 10-bit are now fully supported in hardware (encode and decode) which will significantly reduce power consumption when playing content encoded in these formats. The chip will also allow for improved transition into and out-of clock states (Intel calls this Speed Shift Technology, as shown below).

Intel-Kaby-Lake3

The Core i7-7700K we'll be reviewing today has a base clock of 4.2GHz and a maximum turbo frequency of 4.5GHz (our chip topped out at 4.4GHz under full load). That compares well against the Core i7-6700K (4GHz base, 4.2GHz Turbo), particularly since our 6700K refused to budge above 4GHz under load, despite plenty of thermal and power headroom.

On paper, the Core i7-7700K is only 5% and 7% faster than the 6700K in terms of base clock and turbo clock, but the practical results we saw showed a larger clock gap in practice. Intel's other 7th generation SKUs show slightly larger gaps -- the Core i5-7600K (3.8GHz base, 4.2GHz Turbo) has a 9% higher base clock and an 8% higher boost clock than the Core i5-6600K (3.5GHz base, 3.9GHz Turbo). This trend holds true even at lower TDPs, the Core i5-7400T has a 35W TDP, a base clock of 2.4GHz, and a max boost clock of 3GHz. The 6400T, in contrast, has a 2.2GHz base clock and a 2.8GHz boost clock.

Special mention: Intel's new, unlocked Core i3

A few years ago, Intel launched a 20th Anniversary Pentium (G3258). The diminutive dual-core was positioned like a budget part, at $72, but could hit overclocks of 4.7 - 4.8GHz fairly easily. While that didn't make the core a unilateral winner in every case, it was an intriguing option for overclockers on a budget. Now, Intel is planning to offer an unlocked Core i3 processor, its first ever. The Core i3-7350K will have two cores, four threads, a flat 4.2GHz clock speed, and an unlocked multiplier. Price is set at $162 in 1000-unit quantities.

This compares well against the Core i3-6320, the current top-end Intel Core i3 from the Skylake generation. That core tops out at 3.9GHz and has a list price of $149 - $157. While the Core i3-7350K is considerably more expensive than the Pentium G3258, it's also significantly more capable thanks to higher base clock speeds and Hyper-Threading support. While dual core processors without Hyper-Threading have been pushed to the bargain bin, the Core i3's basic configuration is mirrored in most of Intel's mobile product lineup. With laptops outselling desktops significantly these days, dual-core CPUs aren't going anywhere anytime soon. If Intel's Core i3-7350K can hit the same 4.8GHz clock speeds as the Pentium G3258 it could cement itself as an enthusiast darling.

Our test board: The Asus Strix Z270E Gaming

Every good CPU needs a good motherboard and Asus was kind enough to offer their Strix Z270E Gaming(Opens in a new window) platform for our tests today. This new platform fully supports the BCLCK overclocking that Kaby Lake implements and can run DDR4 memory at up to 3866MHz. Both AMD and Nvidia multi-GPU configurations are supported via the PCI-Express slots (the board technically supports up to three video cards, but the third PCIe slot is only electrically x4. Up to 64GB of memory is supported, though gamers who want to push DRAM speed and capacity may, as always, have to make some trade-offs between the two to ensure system stability. We recommend consulting Asus' memory recommendations before pulling the trigger.

Asus-1

Of the dual M.2 ports supported by the board, both of them can be configured as either PCIe 3.0 x4 devices or as SATA mode devices. If you opt for SATA mode, it means sharing port bandwidth with several of the other SATA ports on the motherboard. USB 3.1 Gen 2 support is provided by Asmedia. The board supports the use of USB 3.1 Gen 2 for both front and rear USB 3.1 connections, meaning you've got one front-mounted port, one rear Type-A, one rear Type-C, and an additional six USB 3.0 ports provided by the native Intel controller.

Wireless and Bluetooth 4.1 support are provided on-board, with support for 802.11ac and both the 2.4GHz and 5GHz bands. The Z270E's SupremeFX audio solution is via the ALC S1220A codec. The integrated LEDs do nothing to improve performance, but they do light up the board nicely (additional board details and photos are available in the slideshow below).

[metaslider id=241963]

We didn't have time to put the Z270E Strix Gaming through its paces as thoroughly as we would've liked, with this launch coming hard on the end of the holiday season. I'd be remiss not to note that our overall experience with the board has been excellent. Early boards with tight launch schedules can be a crapshoot, but the Asus Z270E Strix Gaming is solid, with a well-organized UEFI, a variety of options for overclockers and neophytes alike, and support for automatic overclocking that we plan to revisit at a later date. With a street price set at $199 it's not the cheapest 200-series motherboard on the market, but there's a lot of value here.

Now that we've stepped through the motherboard, CPU, and chipset, let's take a look at overall performance.

Test Setup

It's been a little while since ET published a full CPU review, which meant it was time to throw out old, legacy results and start from scratch. We're still working on building out a new test suite and gathering results in preparation for AMD's Ryzen launch later this quarter, so this specific review is limited to three CPUs in total: The Core i7-7700K, the Core i7-6700K (both tested in the Asus Strix Z270E Gaming motherboard) as well as Intel's 10-core Core i7-6950X and its accompanying Gigabyte GA-X99-Ultra Gaming motherboard.

All of our CPUs were configured with four 8GB sticks of DDR4-3200 courtesy of GSkill(Opens in a new window) (F4-3200C14Q-32GTZ). We had no trouble running the RAM at 3200MHz with Skylake, Kaby Lake, or Broadwell-EP, even though the maximum clock speed was substantially higher than anything these chips are formally rated for. All of our CPUs were tested using Windows 10 patched up to the latest version, with a 750W Antec 80 Plus Gold power supply, a 500GB Samsung 850 EVO SSD, and a Gigabyte GTX 1070 8GB running Nvidia's 376.33 drivers.

The 6950X wouldn't have been my first choice for a direct comparison to the 6700K and 7700K, but it does give us the opportunity to contrast the performance of Intel's standard quad-core + HyperThreading CPUs against a 10-core behemoth running at a lower clock rate (3GHz base, 3.5GHz maximum all-core Turbo). With a 1KU price of over $1700, the 6950X isn't cheap, so it's worth checking where those cores deliver and where they fall short against more conventional CPUs.

Note: While we intended to benchmark both Civilization VI and Ashes of the Singularity, Civilization VI will only store one file of benchmark results for each of its two benchmarks, despite going to the trouble of generating custom names for every benchmark run and informing the end-user that these result files have been saved to disk. This is presumably an accident, since it makes no sense to go to the trouble of creating custom-named log files only to dump the files thereafter, but since we didn't discover this errata until we went to compare the results, we did not have time to retest that game.

Our benchmark results are given below. All three of our Blender Render benchmarks can be downloaded here(Opens in a new window). Each graph within the slideshow can be clicked to open it in a new window.

[metaslider id=241951]

Power Consumption

Our power consumption results need a bit of explanation. When we configured the Core i7-6950X for testing, we noticed dramatically different power consumption, even at idle, depending on whether we configured the system to use Intel's Extreme Memory Profile. Without XMP enabled, the Core i7-6950X idled at 65W and ran all-out at 168W. With XMP enabled, the chip turned in a consistent 107W idle draw, with a 210W system power draw in Prime95. This effect persisted even after we manually checked and configured the CPU to make certain Gigabyte's UEFI settings weren't overriding Intel's preprogrammed Turbo frequencies. We opted to test the 6950X with the same memory configuration and timings we had used for our Asus Strix Z270E Gaming motherboard, since not-using those settings proved to impact the chip's performance in several tests and would not have been a true apples-to-apples comparison.

PowerConsumption

Right away, we see the benefits of Intel's improved 14nm process. Our Core i7-6700K ran at a consistent 4GHz in all our benchmark tests, while our Core i7-7700K preferred a 4.4GHz clock. Intel is pushing a 10% higher clock rate in Prime95, while power consumption for the 7700K is actually down slightly from the 6700K. But -- and this is critical -- it's only down slightly. I'm not running temperature figures at this point because of a configuration issue with my Peltier+air cooler that lowered its overall efficiency, but the data I gathered suggests that the Core i7-7700K runs hotter than the Core i7-6700K, even if the difference isn't very large.

Leaked overclocking results suggest that Intel's decision to use thermal paste instead of solder to connect the 7700K's heat spreader to the die has resulted in poor overall thermal conductivity, and it's not clear how good of an overclocker the core will turn out to be. I suspect the answer is "not very." Intel clearly picked up some performance gains from its new 14nm process, but a careful comparison of its old 6th Gen SKUs to its 7th-gen SKUs suggest that the new chips are between 5-10% faster in the same power envelopes. That's an improvement, certainly, but it's not a very big one. One can't help wondering if Intel could've squeezed another 4-6% out of the chip just by opting for solder.

Conclusions

As much as I'd like to write something exciting about the Core i7-7700K, everything I can think of qualifies as damning with faint praise. It's a solid CPU core with some modest clock speed improvements, a few new media engine capabilities, and a slightly improved power consumption curve. If you're really wanting to build a 4K-capable HTPC with the ability to stream 4K content via Netflix, 7th Generation Core chips are definitely the way to go, and we're downright curious about the upcoming Core i3-7350K.

But the hard truth is, Intel's "Optimization" step doesn't seem to have delivered all that much in the way of concrete benefits. Best-case, Kaby Lake is about 10% faster than Skylake in a modestly improved power envelope. Considering that Skylake launched 18 months ago now, that's not much improvement to deliver given how much time has passed. And Intel, which has a long history of launching its less-impressive chips on weird dates and times (the original Socket 478 iteration of Prescott launched on Super Bowl Sunday, 2004) undoubtedly knows it. Launching a chip this early in the year means that journalists who might have enjoyed spending time with family and friends had to work overtime to get the review done, given that CES kicks off on January 5.

Last week, a rumor spread that Intel was working on a new x86 architecture. I have no inside information on whether this is true, but Intel's CPU performance improvements have been limited to small year-on-year gains since Sandy Bridge launched in 2011. Much of this is due to physics being a great deal less cooperative, and if you compare Intel's performance in the 15W - 35W space the company has delivered much larger gains. That's not much comfort to desktop die-hards who remember when you could count on a new CPU delivering 2x the performance of your last CPU within 24-36 months, and it wouldn't surprise me at this point if Intel was working on a new clean-sheet design.

The Z270 chipset is solid, the Asus Strix Z270E Gaming is a great motherboard, GSkill's DDR4-3200 worked flawlessly with every motherboard we tested, Optane may deliver some game-changing performance in the future, and if you need a new CPU after holding off on upgrading for several years, there's no reason not to upgrade to the Core i7-7700K. That is, of course, unless you'd like to see what AMD is going to deliver with Ryzen this quarter. Given the cost of buying new RAM, new motherboards, and a new CPU, there's a good argument to be made for waiting and seeing a little longer.

Now read: What is Moore's Law?

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Broadwell-EP Cpu AMD CPU Review Core I7-7700K

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