The Intel i7-6700K Review; Skylake Arrives

Author: SKYMTL
Date: August 4, 2015
Product Name: i7-6700K
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While it may not have been apparent due to their dominance in the x86 processor market, Intel has been facing some unique challenges as of late. Their definitive tick / tock cadence of process technology shrinks followed by base architectural changes has been slowing down. 22nm architectures with 3D transistors like Ivy Bridge and Haswell were initially quite difficult to produce while 14nm Broadwell parts were delayed and only launched outside the mobile market over the last few weeks. Now they are already moving on to Skylake, Broadwellís successor but this time around the DIY PC segment will get their hungry little mitts on these processors first.

Intelís approach to Skylakeís launch is indeed an interesting one since unlike previous releases which focused on the notebook and small form factor markets for their initial rollouts, this one will benefit enthusiasts and gamers before everyone else. However, additional details about the core architecture, integrated graphics subsystems and feature support will only be discussed in a few weeks at IDF. That means this review will showcase raw performance but the nuts and bolts which allow these 14nm chips to go about their business will need to remain under wraps for the time being.

According to Intelís own documents, PC gaming has changed from niche market status into something that now drives the PC platform as a whole. With games like Starcraft, DOTA and other titles gaining in popularity and featuring championships that frequently pack stadiums full of people, itís no wonder that Intel has taken notice. With over 1.2 billion people classifying themselves as PC gamers and exponential year over year growth thereís certainly money to be made by launching products which embrace gaming and overclocking.

While we will get into both new 6th generation Core series processors in a bit, itís important to mention the changes which will affect users who want to upgrade. For starters Skylake CPUs boast a new architecture thatís a significant departure from the Haswell and Broadwell generations of yesteryear. Like Haswell, that means a new socket (in this case one with 1151 pins) and a new motherboard will be required. The Z170 series boards will be replacing the venerable Z97 and they will also bring forth a whole raft of upgrade possibilities that weíll go over on the next page.

Gone too is DDR3 as Intel moves to DDR4 across their product range. Not only will this bring higher bandwidth to the table but it should also give the significantly upgraded processor graphics a whole lot more room to operate. DDR4 prices may be high but expect the advent of Skylake and Z170 to usher in a day of more affordable dual channel kits.

For the time being the Skylake lineup will be restricted to a pair of unlocked SKUs: the i7-6700K and i5-6600K. These will be followed up in Q3 2015 by a full range of additional parts to fill out other price points. Expect non-K series CPUs, i3, Pentium and mobile CPUs to quickly arrive after IDF and eventually cascade down into all segments.

The i7-6700K is Intelís new flagship outside their ultra high-end Haswell-E lineup. It boasts a quartet of cores, eight threads courtesy of Intelís Hyper Threading technology and 8MB of Smart Cache. The base clock rings in at an even 4GHz while the Turbo frequency of 4.2GHz remains a bit behind the i7-4790K. Intel has worked hard to bring the Base and Turbo speeds of this chip into close proximity to one another, offering consistent performance regardless of how many threads are being utilized. Like its predecessors, the i7-6700K will be priced at around $350.

Intelís i5-6600K is a more affordable 4-core, quad thread alternative to its higher end sibling and we expect this is the chip many will gravitate towards due to its $250 price point. With that being said, the $100 more expensive processorís additional threads may come in handy within a DX12 environment. Its architectural specifications do however mirror the i7-6700K with the exception of a lack of Hyper Threading and 6MB of Smart Cache in the place of a full 8MB. This CPU is meant to replace the outgoing i5-4690K and boasts identical clock speeds to boot.

Behind the x86 processing stages of these two new chips lies Intelís revamped HD 530-series integrated graphics. While the actual architectural details behind them will remain a mystery for the time being, we do know they will operate at 1150MHz and offer full DX12 compatibility. However, the next generation of Intelís extremely impressive Iris Pro wonít be offered on these unlocked SKUs since most people using them will be using dedicated graphics cards rather than higher end CPU-bound graphics processing capabilities. This situation will likely lead to the Broadwell-series i7-5775C and i5-5765C remaining the solutions of choice for some system integrators while the more expensive K-series Skylake chips will continue to address the needs for enthusiasts and overclockers.

With their expanded graphics stages versus Haswell / Devilís Canyon and higher clock speeds than 14nm Broadwell chips, the i7-6700K and i5-6600K feature TDPs of 91W. That actually represents a very minimal increase over Devilís Canyon while still remaining untouchable in the performance per watt bracket by the best AMD has to offer.

As Intel goes about their tick / tock approach, we have seen a continual 10% performance improvement from generation to generation. Skylake is no different but more significantly, users of slightly older CPUs like the 4770K and 3770K will likely see more significant speedups of 20% and 30% respectively while Sandy Bridge processors will likely be beaten by a good 50%. None of these numbers are anything to sneeze at since theyíve been achieved without vast frequency increases but they arenít exactly earth-shattering either. Much of Intelís hesitation to really put their hair down is likely due to an utter and complete lack of competition from AMD in the $200+ price bracket, not to mention the 14nm manufacturing process' limits. Until we see something different from AMD other than failed GPU compute initiatives, Intel will likely continue down this route.

Alongside the benefits brought about by higher IPC numbers, Intel is also touting a 20-40% graphics improvement over previous generations. This points towards a significant baseline architectural change but thereís certainly not enough for these initial Skylake CPUs to compete against the i7-5775C or other desktop Broadwell processors.

With Skylake, overclockers have been thrown a few more bones with some additional granularity adjustments being thrown into the equation. For example Haswell and earlier generations had their Base Clock tied to a simple ratio of 100MHz, 125MHz or 166Mhz which limited BCLK to a factor of one of those points. Unlocked K-series Skylake chips on the other hand feature 1MHz increments so a full range of speeds can be achieved. Memory adjustments have also been given an upgrade.

Skylake looks like an interesting architecture even though we donít know all that much about its inner workings yet. It is certainly heartening to see Intel cater to the wants of overclockers and games after the late launch of Broadwell. Weíre also going to see Skylake on the market for longer than previous architectures since the upcoming 10nm node shrink has seen its own delays and has been pushed back to sometime in 2017. For those of you wondering what challenges with the 14nm manufacturing process will do to availability, there doesnít seem to be any reason to worry since these processors and their accompanying motherboards will be on retailersí shelves right away.

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