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Overclocking the Core i7-4790K


Can Devil's Canyon deliver?
— 11:14 PM on June 26, 2014

Like lots of things in personal computing, overclocking has progressed mightily since its early days. Back when we first started experimenting on Celerons, CPU performance was a scarce and precious resource, doled out in small increments for hundreds of dollars each. Those of us who dared to violate the specs on our processors were viewed with suspicion by our peers and those in the PC industry alike. Sure, what we were doing wasn't technically illegal, but you'd think it might have been, given how some folks reacted. CPU makers talked about the voiding of warranties and, worse, warned ominously of the dangers of electromigration ending your chip's life early.

None of it slowed us down, of course, because PC enthusiasts saw a chance to grab more of that sweet, sweet computing power essentially for free. Raising the clock speed from 300 to 450 MHz meant 50% more oomph for, you know, decompressing those JPEGs that really fly down the pipe over a V.90 modem. For decoding those beefy 192Kb MP3s. For pushing higher frame rates in QuakeWorld. For, uh, making Outlook Express feel extra snappy.

Yes, you could feel the speed difference in a mail client. Those were dark days.

Back then, we truly needed more speed in the worst way, and overclocking was a means of obtaining what you couldn't buy—either because it was too expensive or just couldn't be purchased.  As a result, a great many PC DIYers overclocked their systems. The "free" extra speed was one advantage of having built your own box.

Somewhere between then and now, overclocking sold out. I know how strange it sounds to hear that a quirky practice, something people do, could succumb to the allure of fame and fortune, but somehow, that's what happened.

Specific products became tailored for overclocking, especially motherboards. Companies introduced "overclocked in the box" video cards, which weren't overclocked at all but borrowed the word shamelessly. Meanwhile, overclocking became a competitive endeavor, complete with world records, celebrity practitioners, and corporate sponsors. Liquid nitrogen got involved. Over time, even Intel and AMD got into the act, creating "overclockable" versions of their chips with unlocked multipliers, available for a slight price premium.

The real kiss of death had to be when "overclockers" cooled and hardened into one of the handful of terms used by product marketing people to describe the PC market. You've got your "mainstream" buyers, your "enthusiasts," "gamers," and "overclockers." Individual products are built to appeal specifically to each of these segments. I've seen the PowerPoint slides. I've gotta admit, I've been doing this job for a long time, but I don't know what those terms actually mean. I'm pretty sure that means they're perfectly integrated into the corporate lexicon, which is about talking without saying things.

All of which leads me, implausibly, to Devil's Canyon.

You see, Intel says the new CPUs under this code-name are intended for "overclockers." Does that mean me? Or does it mean some guy with a LN2 pot, a modified motherboard, and a stack of six chips to try while pursuing the SuperPi world record? Honestly, I'm confused on that point. I dunno whether I qualify for this product's target demo.

Then again, as a PC enthusiast and tinkerer, I don't much care either way. I just want to know if there's more free speed to be squeezed out of these things. So let's have a look.

The Devil's Canyon chips
Under the metal cap of a Devil's Canyon processor is the same 22-nm Haswell silicon that drives any other recent Intel Core i5/i7 CPUs. The differences are at the package level, and the biggest one is literally right under that cap: a new thermal interface material, or TIM, between the cap and the chip. Intel switched to a different thermal interface with its first 22-nm chips, and some folks blamed the new TIM for the Ivy Bridge chips' unwillingness to overclock as well as the 32-nm Sandy Bridge processors before them. They claimed the prior TIM arrangement, known as fluxless solder, transferred heat more efficiently. Devil's Canyon has switched to a third option, a "next-generation" polymer TIM known affectionately as NGPTIM. Its goal is to transfer heat more efficiently between the CPU and the cap above it—and thus to the cooling solution sandwiched on top of it all.

Is the stock TIM for Ivy Bridge and Haswell really a problem? I dunno. Many substances (even toothpaste) can serve competently as the thin layer ensuring solid contact between two surfaces. This TIM issue is a matter of debate, but Intel does seem to have validated its critics by adopting another TIM in these new products.


The Core i7-4770K (left) and the "Devil's Canyon" Core i7-4790K (right)

The other change to the Devil's Canyon parts is visible in the picture above. The package has a modified power delivery arrangement, with more capacitors than in the regular Haswell substrate. Intel says the added caps will "smooth power delivery to the die," which in turn should increase stability and thus frequency headroom. That's the theory, at least.

To its credit, Intel went off of its established roadmap and made these tweaks to Devil's Canyon pretty quickly in direct response to the perceived desires of PC enthusiasts. These products are an olive branch, the first step in a renewed commitment to desktop CPUs.

Model Base
clock
Max
Turbo
clock
Cores/
threads
L3
cache
Intel HD
Graphics
Max
graphics
clock
TDP Price
Core i7-4790K 4.0GHz 4.4GHz 4/8 8MB 4600 1250MHz 88W $339
Core i7-4770K 3.5GHz 3.9GHz 4/8 8MB 4600 1250MHz 84W $339
Core i5-4690K 3.5GHz 3.9GHz 4/4 6MB 4600 1200MHz 88W $242
Core i5-4670K 3.4GHz 3.8GHz 4/4 6MB 4600 1200MHz 84W $242

The two models highlighted in bold in the table above are Devil's Canyon parts. Only these two products will get the special treatment, and both of them belong in the unlocked, overclocking-friendly K-series lineup.

The Core i7-4790K essentially replaces the 4770K at the same price, and if you have zero plans for overclocking your CPU, the 4790K is still worthy of your attention. Intel has raised the base and peak Turbo clock speeds by 500MHz, so the 4790K's baseline operating frequency is an even 4GHz. This is Intel's first 4GHz desktop processor, and more importantly, this clock speed bump ensures the largest desktop CPU performance increase we've seen in several generations (at stock speeds, at least.)

The 4690K is less exciting, since it's just 100MHz faster than the 4670K before it.

Both of these chips are rated for 88W of peak power draw, up 4W from the prior models. Intel says any motherboard based on the new Z97 chipset ought to support them. Happily, the firm has allowed older Z87 boards to host Devil's Canyon processors, as well, provided they can deliver the additional power needed. We expect most mobo makers to provide firmware updates to enable support.

Oh, one more thing. Intel has evidently been listening to our complaints on another front. The ARK listings for the 4690K and 4790K say these CPUs support Haswell's new TSX instructions for transactional memory and VT-d for virtualized I/O. In a baffling move, the older K-series parts didn't support these advanced features, apparently because "enthusiasts" and "overclockers" shouldn't care about... performance? I dunno. Like I said, baffling, but happily, Intel made things right in the new models.