Skylake Review: Intel’s 6th-gen CPU arrives with nice presents for gamers and enthusiasts

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After an eternity of hype, innuendo and rumors, Intel’s Core i7-6700K, code-named “Skylake,” is finally here—and it’s actually worth the wait. But only if you have realistic expectations, not those built up on months of leaked “performance” numbers from websites you have to use Google Translate to read.

If you came into this review expecting Skylake to be “40 percent faster” than its predecessor in all things, like the rumors said, you’re already set up for disappointment.

Well, don’t be.

Skylake is indeed faster than Haswell, but despite the “tock” label, it’s still just an evolutionary step forward. Skylake isn’t just about the CPU, though—it’s an entire platform, and that’s where this 6th-gen part moves us forward.

Meet Skylake

First you need to know what Skylake is. Intel’s 6th-generation CPU, Skylake brings DDR4 memory to the mainstream as well as improved overclocking features, better integrated graphics performance, and a new chipset.

There have been leaked details of Intel’s entire desktop line, but those are still unofficial and, frankly, pretty wrong so far. On Wednesday in Cologne, Germany, at Gamescom,  the world’s largest game convention, Intel officially unwrapped only two Skylake desktop CPUs. Both are aimed squarely at gamers and PC enthusiasts.

corei7 models
Intel is only introducing two models today, but you can bet it’s just the first few drops of a storm.

While this review drops as much info as I have today along with performance data I’ve gleaned from testing the chip, you won’t be learning any details of what’s under that shiny metal lid. That’s because I don’t know.

In an unusual launch for Intel, the company isn’t saying much about Skylake other than what we can tell externally and the basics of it. We don’t know how many transistors are inside, what the die size is, or what Intel even did to Skylake over Haswell on a low level. I don’t even have an official obligatory, colorful image of the Skylake die that you usually see on launch day.

All of that info is being reserved for the Intel Developer Forum that starts on August 18 in San Francisco, so tune back in a couple of weeks to find out what’s under the lid.

cpuscomparedGordon Mah Ung
From left to right we have a 2nd gen Core i7-2700K, a 4th Core i7-4790K, the 6th gen Skylake an the gigantic Haswell-E Core i7-5960X chip.

Yes, you’ll need new RAM too

To be fair, Intel isn’t keeping everything a secret and has revealed some important changes for the chip.

The most in-your-face change is the new socket that’s incompatible with today’s CPUs. That means you won’t drop a Skylake CPU into your Haswell motherboard, and you won’t be dropping your Haswell processor into a Skylake mobo.

Before you start groaning that Intel is playing the forced-obsolescence card, you should remember that Skylake introduces DDR4 to the mainstream. While it might feasible to design a motherboard that will work with both, making a cleaner break is usually the better choice to reduce confusion. Skylake does actually support DDR3L RAM, but that’s for servers and laptops. The DDR3 in most people’s desktop systems won’t work with it. You just need to come to grips with that: If you decide to build a new Skylake desktop, you will need to buy new RAM, too.

The good news is the price of DDR4 isn’t the deal-breaker it was when first introduced with Intel’s Haswell-E CPUs last year. Today, you can get 8GB of DDR3/1333 for $40, while 8GB of DDR4/2133 costs $50.

You will need two of those modules for dual-channel support, because Skylake, like the last few consumer-grade chips, needs two modules to operate at its maximum bandwidth.

For those who always felt the 32GB of maximum RAM in the mainstream Haswell-based desktops was a limitation, Skylake’s use of DDR4 means you can get 64GB of RAM into your rig without having to step up to a pricier Haswell-E system.

dsc00476Gordon Mah Ung
Intel’s 6th gen Skylake CPU will require a new LGA1150 socket that is incompatible with Haswell’s LGA1151.

It’s overclocking-friendly

Remember when Intel trumpeted that moving the circuits that govern the power for the processor into the CPU was a big leap forward for Haswell? Well, maybe it wasn’t, because it’s now been 86’ed with Skylake.

The Fully Integrated Voltage Regulator (FIVR) was controversial from the beginning. When introduced with Haswell, overclockers and motherboard makers complained that it put a laptop architecture in the driver’s seat, to the detriment of desktops.

While we probably won’t know why FIVR missed the Skylake boat until IDF, Intel at least acknowledges that motherboard makers and overclockers should be happier this time. In fact, the company said it’s produced one of its most “exciting” chips for overclockers in a long time.

skylakeGordon Mah Ung

If you think of overclocking as turning a bunch of interconnected knobs until you can run your CPU at the highest clock speed possible, Skylake offers far finer adjustments. For example, with Core i7-4790K, the base clock knob allowed settings of only 100MHz, 125MHz and 166MHz. With Skylake, that knob now changes in 1MHz increments, which means overclockers can tune in their highest clock speeds with more granularity.

Memory overclocking is another prominent feature. Skylake supports overclocked RAM up to DDR4/4133 speeds, and with finer resolution, too.

Keep reading—we’re getting to the good stuff, about overclocking!

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Skylake’s new case sticker

How well does it really overclock?

Rather than trying to overclock my single CPU sample on an unfamiliar chipset and motherboard and draw a conclusion that would be useful, wouldn’t you rather know the results from someone who’s already tried overclocking a ton of them?

That’s what motherboard company Asus has done to help tune its automatic overclocking routines for Skylake.

Taking the results of what it achieved after trying to overclock trays of CPUs, Asus produces its pre-launch forecast that’s usually an accurate predictor for what consumers can overclock to reliably.

You can basically expect to hit 4.6GHz to 4.7GHz with a retail Core i7-6700K chip, the company says. The absolute best samples will push 4.8GHz. That’s actually a slight improvement over Haswell, which topped out at 4.5GHz on liquid cooling for most. Higher usable overclocks were few and far between, and many had worse overclocking experiences with Haswell, so Skylake is indeed an improvement

The only real disappointment will be for those who bought into the leaked stories that Skylake would hit 5.2GHz on air cooling—not even liquid cooling—and believed it would translate into an experience for all. If Asus’ data is correct (and there’s nothing to indicate otherwise), the only 5GHz overclocks will live in your memories of Intel’s Sandy Bridge CPUs.

As a consolation prize, you should know Asus’ forecast says Skylake CPUs can hit DDR4/3600 clock speeds with all four DIMM slots filled on a good motherboard (ahem—from Asus, natch).

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We used this Asus Z170-Deluxe with the new Z170 chipset for the bulk of our testing.

The unsung hero: The Z170 chipset

The real star here is the Z170 chipset. The Robin to Skylake’s Batman, Z170 is probably just as important for what it finally fixes in the limitations of the chipset it replaces. Like Haswell, Skylake features just 16 PCIe Gen 3 lanes in the CPU. Any additional PCIe lanes come from the chipset. In Haswell’s Z87 and Z97 chipset, the limit was just 8 PCIe Gen 2 lanes, which hadn’t changed since 2011’s Sandy Bridge chipset.

In 2011 that was probably fine, but today, that’s not enough expansion for modern PCs with fast M.2 drives, SATA Express drives, and USB 3.1. Even worse, to get more bandwidth to run high speed devices such as, say Intel’s 750-series SSD, you had to steal bandwidth from the GPU.

With Z170, Intel is finally, finally stepping up and giving the chipset  up to 20 PCIe Gen 3 lanes. Because increasing the water pipes to your home without increasing the size of the water mains would be worthless, Intel is also doubling the interconnect from the CPU to the chipset. The new DMI 3.0 in Z170 offers up to 40Gbps using a x4 PCIe Gen 3 link. The Z97 used a 20Gbps x4 link PCIe Gen 2 link.

skylake slide2
Skylake’s biggest contribution to desktops will be the Z170 chipset that adds PCIe Gen 3.

The upshot is that with Z170, you can run your graphics card at full bandwidth while still having a super-fast PCIe or M.2 SSD or multiple SATA SSDs along with your your 10Gbps USB 3.1 devices, without sacrificing performance as you would with older chipsets. And no, it doesn’t actually support native USB 3.1. That’s added through third-party chipsets only.

This may seem like a long discussion of plumbing, but believe me, the Z170 is a welcome refresh for Intel’s consumer chipsets, one that’s long overdue.

Numbers don’t lie—keep reading for hard performance data on Skylake.

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Performance

Let’s get on to how well Skylake actually performs. For my testing, I used a new Asus Z170-Deluxe motherboard, 16GB of Corsair DDR4/2666, and a 240GB Kingston HyperX SSD. For the comparison I used the same Haswell Core i7-4790K and Broadwell Core i7-5775C from the last review. All three were run with integrated graphics, as the IGP is an important metric Intel is pushing.

Don’t worry, I did do some game testing with a real GPU too. I also dug up an older Sandy Bridge Core i7-2600K in an Asus Z77-Deluxe system for some of the testing but didn’t run our complete benchmark suite against it.

One last system I threw into the mix was AMD’s A10-7870K running 16GB of DDR3/1600. Yeah, AMD fans will crow a $140 CPU shouldn’t be rubbing shoulders with CPUs that all exceed $340, but this comparison is to see just how Intel’s graphics have come against a budget part. AMDers should also expect Skylake graphics cores to be slung their way when Intel introduces Skylake into Core i3 CPUs.

cpumodels
For some context on Intel’s top-end mainstream CPUs, here’s the pertinent details form Sandy Bridge to Skylake.

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