Core i7-6700K CPU Review

[nextpage title=”Introduction”]
We tested the Core i7-6700K CPU, the new high-end, sixth-generation CPU from the Intel Core i family, codenamed “Skylake.” It has four physical cores (plus four virtual ones due to the Hyper-Threading technology) running at 4.2 GHz with turbo clock up to 4.2 GHz, and is manufactured with 14 nm lithography. Let’s see if is it superior to a high-end CPU from the fifth generation, the Core i7-5775C.
The sixth generation of the Core i CPUs from Intel is called “Skylake” and is, like the “Broadwell” (fifth generation) models, manufactured under 14 nm process. Intel uses a “tick-tock” chronogram, where the “tick” represents a new manufacturing process, while the “tock” is a new microarchitecture, using the same process from the earlier generation. Therefore, the “Skylake” architecture represents a “tock,” because it uses the same 14 nm process from the fifth generation, but with a new microarchitecture.
One of the main changes of this new microarchitecture is the compatibility with DDR4 memories (former CPUs were compatible only with DDR3 memories). Because of this, the Skylake desktop processors use a new socket, called LGA1151, which is not compatible with former CPUs.
We already tested two entry-level CPUs from this new family, the Pentium G4400 and the Core i3-6100.
We choose to make most of the benchmarks using a high-end video card, with the integrated video disabled. Being a high-end CPU for desktop computers, the Core i7-6700K will be used, most of the times, with a “real” video card; most users that are looking for a CPU on this price range prefer not to use the video card. Anyway, we also ran some benchmarks to test the integrated video performance.
We compared the performance of the Core i7-6700K to its fifth-generation predecessor, the Core i7-5775C, which we tested before. We did not include any AMD processor simply because it does not offer any competitor to the Core i7-6700K. The most expensive CPU from AMD, the FX-9590, costs less than half the price of the Core i7-6700K, so it would not be a fair (or useful) comparison.
Figure 1 unveils the Core i7-6700K CPU, aside with the Core i7-5775C we used on our tests.

Figure 1: the Core i7-5775C (at the left) and the Core i7-6700K (at the right)

Figure 2 shows the bottom of both CPUs. Notice that the side chamfer are located at different positions, which prevents an LGA1151 to be installed in an LGA1150 socket and vice-versa.

Figure 2: the bottom of the Core i7-5775C CPU (left) and the Core i7-6700K (right)

Let us compare the main specs of the reviewed CPUs in the next page.
[nextpage title=”The Reviewed CPUs”]
In the tables below, we compare the main features of the CPUs included in our review.

CPU	Cores	HT	IGP	Internal Clock	Turbo Clock	Core	Tech.	TDP	Socket	Price
Core i7-6700K	4	Yes	Yes	4.0 GHz	4.2 GHz	Skylake	14 nm	91 W	LGA1151	USD 380
Core i7-5775C	4	Yes	Yes	3.3 GHz	3.7 GHz	Broadwell	14 nm	65 W	LGA1150	USD 372

Prices were researched at Newegg.com on the day this article was published.
TDP means Thermal Design Power, the maximum amount of heat the CPU can dissipate.
Below you can see the memory configuration for each CPU.

CPU	L2 Cache	L3 Cache	Memory Support	Memory Channels
Core i7-6700K	4 x 256 kiB	8 MiB	Up to DDR3L-1600 or DDR4-2133	Two
Core i7-5775C	4 x 256 kiB	6 MiB	Up to DDR3-1866	Two

[nextpage title=”How We Tested”]
During our benchmarking sessions, we used the configuration listed below. Between our benchmarking sessions, the only variable device was the CPU being tested, besides the motherboard and memory, which had to be replaced to match the different CPUs.
Hardware Configuration

• Motherboard (socket LGA1151): ASRock Fatal1ty Z170 Gaming K6+
• Motherboard (socket LGA1150): ASRock Z97 Extreme4
• CPU Cooler: Intel
• Memory (DDR3): 8 GiB DDR3-2133, two G.Skill Ripjaws F3-17000CL9Q-16GBZH 4 GiB memory modules configured at 2,133 MHz
• Memory (DDR4): 8 GiB DDR4-2400 two G.Skill Ripjaws 4 F4-2400C15Q-16GRR 4 GiB memory modules configured at 2133 MHz
• Boot drive: Kingston HyperX Savage 480 GB
• Video Card: GeForce GTX 980 Ti
• Video Monitor: Philips 236VL
• Power Supply: Corsair CX750

Operating System Configuration

• Windows 7 Home Premium 64-bit
• NTFS
• Video resolution: 1920 x 1080 60 Hz

Driver Versions

• NVIDIA driver version: 359.06
• Intel Inf chipset driver version: 10.0

Software Used

• 3DMark 1.5.915
• Adobe Photoshop CC + Retouch Artist Speed Test 1.0
• Cinebench R15
• DivX 10.2.4
• DVD Shrink 3.2
• Media Espresso 6.7
• PCMark 8 2.4.304
• Dirt Rally
• Dying Light
• Fallout 4
• GTA V
• Mad Max

Error Margin
We adopted a 3% error margin. Thus, differences below 3% cannot be considered relevant. In other words, products with a performance difference below 3% should be considered as having similar performance.
[nextpage title=”PCMark 8″]
PCMark 8 is a benchmarking software that uses real-world applications to measure the computer performance. We ran three tests: Home, which includes web browsing, writing, light gaming, photo editing, and video chat tests; Creative, that includes web surfing, video editing, group video chat, video conversion, and gaming; and Work, which runs tasks such as writing documents, web browsing, spreadsheets, editing, and video chatting. Let’s see the results.

The Core i7-6700K was 10% faster than the Core i7-5775C on the Home benchmark.

On the Creative benchmark, the Core i7-6700K reached a score 8% higher than the Core i7-5775C.

On the Work benchmark, the Core i7-6700K was 6% faster than the Core i7-5775C.
[nextpage title=”3DMark”]

3DMark is a program with a set of several 3D benchmarks. Fire Strike benchmark measures DirectX 11 performance and is targeted to high-end gaming computers. Sky Diver also measures DirectX 11 performance, and is aimed on average computers. The Cloud Gate benchmark measures DirectX 10 performance. The Ice Storm measures DirectX 9 performance and is targeted to entry-level computers, so we did not include it on our comparison.

Keep in mind that we used a GeForce GTX 980 Ti video card on all tests.

On the Fire Strike benchmark, the Core i7-6700K was not significantly faster than the Core i7-5775C.

On the Sky Diver benchmark, the Core i7-6700K was 9% faster than the Core i7-5775C.

On the Cloud Gate benchmark, the Core i7-6700K was 11% faster than the Core i7-5775C.

[nextpage title=”Photoshop CC and Cinebench R15″]

Photoshop CC

The best way to measure the performance of a CPU is by using real programs. The problem, of course, is to create a methodology that offers precise results. For Photoshop CC, we used a script named “Retouch Artist Speed Test,” which applies a series of filters to a standard image and gives the time Photoshop takes to run all of them. The results are given in seconds, so the less, the best.

In this test, the Core i7-6700K was 11% faster than the Core i7-5775C.

Cinebench R15

Cinebench R15 is based on the Cinema 4D software. It is very useful to measure the performance gain obtained by the presence of several processing cores while rendering heavy 3D images. Rendering is an area where a bigger number of cores helps a lot, because usually this kind of software recognize several processors (Cinebench R15, for example, can use up to 256 processing cores).
We ran the CPU benchmark, which renders a complex image using all the processing cores (real and virtual) to speed up the process. The result is given as a score.

Here the Core i7-6700K was 29% faster than the Core i7-5775C.
[nextpage title=”Video encoding”]

DivX

We used the DivX converter, a tool included in the DivX package, in order to measure the encoding performance using this codec. The DivX codec is capable of recognizing and using all available cores and the SSE4 instruction set.
We converted a Full HD, six-minute long .mov video file into a .avi file, using the “HD 1080p” output profile. The results below are given in seconds, so the lower the better.

On DiVX encoding, the Core i7-6700K was 17% faster than the Core i7-5775C.

DVDShrink

DVDShrink is an old but still very useful program to “shrink” video DVDs that have more than 4.7 GiB of data to fit single-layer DVD media. We used it to compress the DVD of “The Lord of the Rings: The Fellowship of the Ring” DVD to 4.7 GiB. The results below are given in seconds, so the lower the better.

In this test, the Core i7-6700K was 15% faster than the Core i7-5775C.

Media Espresso

Media Espresso is a video conversion program that uses the graphics processing unit of the video engine to speed up the conversion process. We converted a 1 GiB, 1920x1080i, 23,738 kbps, .mov video file to a smaller 320×200, H.264, .MP4 file for viewing on a smartphone. The results below are given in seconds, so the lower the better.

Here the Core i7-6700K was 12% faster than the Core i7-5775C.
[nextpage title=”Gaming Performance”]

Dirt Rally

Dirt Rally is an off-road racing game released in April 2015, using Ego engine. To measure performance using this game, we ran the performance test included in the game, in 1920 x 1080 (Full HD) resolution and image quality configured as “high” and MSAA off.
The results below are expressed in frames per second (fps).

In this game, the Core i7-5775C was 18% faster than the Core i7-6700K.

Dying Light

Dying Light is an open-world horror game launched in January 2015, using the Chrome Engine 6. We tested the performance at this game with quality options at “high” and Full HD resolution, measuring three times the frame rate using FRAPS.
The results below are expressed in fps and they are the mean between the three collected results.

In this game, both CPUs performed similarly.

Fallout 4

Fallout 4 is the newest launch from the popular RPG franchise, being launched in 2015. It uses the Creation engine. We tested the performance in this game on its first scene, with the quality options as “ultra” and Full HD resolution, measuring the framerate with FRAPS three times.
The results below are expressed in fps and they are the mean between the three collected results.

In this game, the Core i7-6700K performance was also the same of the Core i7-5775C.

Grand Theft Auto V

Grand Theft Auto V, or simply GTA V, is an open-world action game released for PCs in April of 2015, using the RAGE engine. In order to measure the performance on this game, we ran the performance test of the game (the part the camera follows the plane), measuring the framerate with FRAPS. We ran GTA V at Full HD, with image quality set to the “very high” and MSAA x2.

The results below are expressed in frames per second.

On GTA V, both CPUs had similar performances as well.

Mad Max

Mad Max is an open-world action game launched in September of 2015, using the Avalanche engine. In order to measure the performance using this game, we ran its intro, measuring the framerate with FRAPS three times. We ran the game at Full HD, with image quality set as “high.”

The results below are expressed in fps and they are the mean between the three collected results.

In this game, both CPUs also had the same performance.

[nextpage title=”Integrated video performance”]
The Core i7-6700K used the Intel HD Graphics 530 graphics engine, which is the “mainstream” engine of the sixth generation Intel CPUs, being actually the same engine found on the Core i3-6100. On the other hand, the Core i7-5775C uses the Iris Pro 6200 engine, which is a “professional” graphics engine from Intel.
To check the performance of the Core i7-6700K integrated video, we ran the 3DMark with the integrated video only, removing the independent video card from the computer.

On the Fire Strike benchmark, the Core i7-5775C video engine was 41% faster than the Core i7-6700K’s.

On the Sky Diver benchmark, the Core i7-5775C’s integrated video was 20% faster than the Core i7-6700K’s.

On the Cloud Gate benchmark, the Core i7-5775C was 15% faster than the Core i7-6700K.

[nextpage title=”Overclocking”]
The Core i7-6700K has an unlocked clock multiplier, which means it is possible to overclock it just by changing the multiplier. Besides that, the socket 1151 processors have its base clock independent from the clock of the buses, so it is possible to overclock it also by raising the base clock.
In quick tests, we managed to run the Core i7-6700K with stability (we tested it with Prime95) up to 4.4 GHz, with 100 MHz base clock and 44x multiplier, with all standard voltages. At 4.5 GHz, the CPU was not completely stable.
Anyway, keep in mind that this value was obtained with the standard cooler, not changing any voltage configuration. So, if you use a more powerful cooler and change the voltages (and other advanced options), you may reach a higher overclocking limit.[nextpage title=”Conclusions”]
The Core i7-6700K reached the market under heavy spectating, after the delay of the fifth generation CPUs. Actually, the “Skylake” (sixth generation) CPUs were launched almost simultaneously with the “Broadwell” (fifth generation) ones, considering that those last ones had a few models and little availability. So, the rumors that the “Broadwell” models were never tough for desktop computers in large scale seem to be correct.
When we tested the Core i7-5775C (fifth-generation high-end model), we concluded that it brings almost no performance gain compared to the former generation (except for the integrated video, that was more sophisticated.) Now, comparing the new high-end model, the situation is a little different.
The Core i7-6700K was, on average, between 10% and 20% faster than the Core i7-5775C, achieving a performance boost of 29% on Cinebench, which is a hint that Intel improved the multi-tasking performance. Costing the same of the former model, the Core i7-6700K is an excellent choice for users that need brute processing power—users that work professionally on video editing, for example.
For the home user, however, the situation is different. On gaming, we did not see any performance improvement, which means that a high-end video card is still a best investment than buying a high-end CPU. So, if you will not professionally use you computer for CPU-demanding tasks, the Core i7-6700K has not a good cost/benefit ratio.