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.

Our attempt at overclocking the 4790K

I wanted to see what a regular dude could get out of the 4790K when overclocking, so I used a fairly typical sort of desktop PC setup, pictured below on our nifty open-bench platform.

That’s an Asus Z97-A motherboard, which Geoff reviewed not long ago, and a Thermaltake NIC C5 dual-fan air cooler. Nice stuff, but not the most expensive gear by any means. That’s the sort of thing we’d recommend in one of our System Guide builds.

My approach to overclocking this thing was simple. I used the firmware to do everything, not Windows tweaking software, and configured all four of the cores to run at the same speed. Then I raised the multiplier in order to change the clock speed. I fed the chip more core voltage as needed in order to improve stability. There are a number of secondary voltage settings one can tweak in order to increase the odds of a stable result, but I didn’t mess with them. Asus’ firmware auto-adjusts those voltages to some degree. I left those settings in “Auto” mode and accepted the extra help. Oh, and I cranked the CPU cooler’s fans to their top speed and used the “Turbo” cooling profile in the Z97-A firmware.

I then tested stability in Windows by running Prime95 and using Asus’ AI Tweaker software to monitor the CPU’s state.

After a little trial and error, I was able to get our sample of the i7-4790K running all four cores stable at 4.6GHz with 1.375V. The Asus utility reported that the CPU was using 141W under load, a pretty dramatic increase from the 88W used at the stock voltage and frequency. With the NIC C5 fan cranked, the CPU temperatures settled in at about 71°C. The cooler’s fans were spinning at around 2125 RPM, and as a result, they buzzed and whined very audibly with Prime95 going.

I then tried rebooting and pushing to 4.8GHz, but the system quickly locked. I dialed back to 4.7GHz, but still, no dice.

In the end, I had to push the core voltage up to 1.45V in order to get something approaching reasonable stability at 4.7GHz. The system would run Prime95 at those settings. AI Tweaker reported the CPU power draw ar 157W, but I don’t think I trust that assessment. The NIC C5 is rated for 230W of cooling capacity, and the 4790K at 1.45V appeared to be right on the edge of what the cooler could handle. The CPU temperature creeped up slowly over time. After about 10 minutes, CPU temps ranged into the mid to high 80s Celsius, and then the Blue Screen of Death made an appearance.

Also, throughout the load test, I could hear the system reporting USB disconnects and reconnects, apparently involving the mouse and/or keyboard. Funky.

The 4790K was stable enough at 4.7GHz to run some benchmarks, but I’d say 4.6GHz is the more reasonable overclocking limit for daily use, unless you have a much beefier cooler than this one. The amount of extra voltage needed—and the resulting thermal load—isn’t worth it.

For comparison, I then dropped my year-plus-old pre-release sample of the Core i7-4770K into the same system and cranked up its clocks. Guess what? It was happy to run at 4.7GHz using only 1.4V, a smidgen less voltage than our Devil’s Canyon sample required. I tried to push higher, to 4.8GHz at 1.45V, but the 4770K wasn’t having it. In the end, the 4770K was a little more comfortable at 4.7GHz than the 4790K, but the two were essentially equivalent in terms of max stable clock speeds. The temperatures of the two CPUs were comparable under load, too, although the 4770K was getting 0.05V less juice.

Of course, we’re comparing just two pre-production samples in a world of possibilities, so your mileage may vary. Heck, it almost certainly will vary somewhat. I should note, though, that Nate’s 4790K peaked at 4.7GHz, Marco’s at 4.8GHz, and Hilbert’s at 4.7-ish. So we are not alone on this front.

Anyhow, let’s tale a quick look at how the 4790K performs, both at its stock speeds and overclocked.

Our testing methods

The test systems were configured like so:

Processor AMD FX-8350 AMD A10-7850K Motherboard Asus Crosshair V Formula Asus A88X-PRO North bridge 990FX A88X FCH South bridge SB950 Memory size 16 GB (2 DIMMs) 16 GB (4 DIMMs) Memory type AMD Performance Series DDR3 SDRAM AMD Radeon Memory Gamer Series DDR3 SDRAM Memory speed 1600 MT/s 2133 MT/s Memory timings 9-9-9-24 1T 10-11-11-30 1T Chipset drivers AMD chipset 13.12 AMD chipset 13.12 Audio Integrated SB950/ALC889 with Realtek 6.0.1.7233 drivers Integrated A85/ALC892 with Realtek 6.0.1.7233 drivers OpenCL ICD AMD APP 1526.3 AMD APP 1526.3 IGP drivers – –

Processor Core i7-3770K Core i7-4770K Core i7-4790K Motherboard Asus P8Z77-V Pro Asus Z97-A North bridge Z77 Express Z97 Express South bridge Memory size 16 GB (2 DIMMs) 16 GB (2 DIMMs) Memory type Corsair Vengeance Pro DDR3 SDRAM Corsair Vengeance Pro DDR3 SDRAM Memory speed 1600 MT/s 1600 MT/s Memory timings 9-9-9-24 1T 9-9-9-24 1T Chipset drivers INF update 10.0.14 iRST 13.0.3.1001 INF update 10.0.14 iRST 13.0.3.1001 Audio Integrated Z77/ALC892 with Realtek 6.0.1.7233 drivers Integrated Z97/ALC892 with Realtek 6.0.1.7233 drivers OpenCL ICD AMD APP 1526.3 AMD APP 1526.3

They all shared the following common elements:

Hard drive Kingston HyperX SH103S3 240GB SSD Discrete graphics XFX Radeon HD 7950 Double Dissipation 3GB with Catalyst 14.6 beta drivers OS Windows 8.1 Pro Power supply Corsair AX650

Thanks to Corsair, XFX, Kingston, MSI, Asus, Gigabyte, Intel, and AMD for helping to outfit our test rigs with some of the finest hardware available. Thanks to Intel and AMD for providing the processors, as well, of course.

Some further notes on our testing methods:

The test systems’ Windows desktops were set at 1920×1080 in 32-bit color. Vertical refresh sync (vsync) was disabled in the graphics driver control panel.

The tests and methods we employ are usually publicly available and reproducible. If you have questions about our methods, hit our forums to talk with us about them.

Rendering and video encoding

Please note that I’ve left the overclocked 4770K at 4.7GHz out of the test results below. That’s simply because it performs exactly the same as the 4790K at 4.7GHz. They’re the same Haswell silicon. I just wanted to keep things simple. Also, I’ve included the two AMD processors solely for reference. They’re AMD’s fastest CPUs in its “extreme” and high-volume desktop platforms (save for those crazy 220W FX chips), but neither one costs as much as a 4790K, so they’re not direct competitors.

Like I said earlier, the 500MHz clock speed boost for the 4790K versus the 4770K is a fairly notable generational increase. Overclocking the thing adds another step up in performance, but remember that it comes at the expense of nearly twice the power consumption (and probably more cooling noise, as a result.)

Crysis 3









If you just glanced at the FPS average in our gaming test, you’d say all of these CPUs must be GPU-limited and therefore I must be a bozo for testing in this fashion. I won’t dispute the bozo thing, but a closer look at the individual frame rendering times will tell you there’s a real difference between these CPUs.

To get smooth gameplay, you want to eliminate momentary slowdowns. As you can see in the frame time plots, those slowdowns are present in a few places during the course of our test session—mainly as I’m shooting dudes with exploding arrows.

Our more sensitive frame-time-focused metrics capture the differences between the CPUs quite nicely. Flip through the results for our “badness” metric, which looks at time spent beyond various thresholds. The 4790K spends less than half the time that the 4770K does working on frames that take longer than 33 milliseconds to produce—and at 4.7GHz, those long frame rendering times are further reduced. I could feel the difference during play-testing—not always, but consistently in the same spots during combat when things were exploding onscreen. The 4.7GHz CPU felt best, followed by the stock 4790K. Even at the very same FPS average, the faster CPU produces measurably and subjectively smoother gameplay.

These aren’t the dark days of computing any longer, but there’s still something to be said for having the fastest per-thread performance possible.

Conclusions

I said earlier that I don’t know who exactly is Devil’s Canyon’s target market. Now that you’ve seen the overclocking results, perhaps you can understand my dilemma. Our review sample doesn’t appear to have any more headroom than our year-plus-old Core i7-4770K. Others in the press have seen the same. If the overclocking tweaks in Devil’s Canyon are aimed at the average DIY PC builder, it’s mighty tempting to conclude that these changes are pretty much pointless.

You know, because there’s no apparent point to them.

When I let slip on Twitter that Devil’s Canyon overclocking didn’t look much different from Haswell overclocking, I got a reply from one particularly vocal Intel employee who told me, essentially, two things. One, wait for the production units and see how they do overall. And two, the big gains will come when “overclockers” find those special, magic chips capable of especially high clocks. Those should happen more often with Devil’s Canyon.

Fair points, I suppose, but again: I’m not that guy with a liquid helium pot and a stack of chips to test. If you’re not, either, then perhaps the new TIM and capacitor layout won’t mean much to you.

Then again, Devil’s Canyon chips have juuust started hitting retail shelves here in the U.S. Perhaps we’ll see something different out of the production parts on a wider scale. We should know more very soon, as folks start dropping them into their systems. I just wouldn’t count on any miracles, given what we’ve seen here.

Fortunately, you can count on the Core i7-4790K delivering a very nice clock frequency bump over the 4770K at stock speeds—for the exact same price. And both Devil’s Canyon parts come with TSX and VT-d enabled, making the choice to go with an unlocked K-series penalty-free. Sorta makes me think Devil’s Canyon’s most receptive audience may be folks who don’t overclock at all. So the news is good, even if it’s not quite what we expected.

The even better news, I think, may be another CPU that Intel is introducing any day now: the Pentium G3258 Anniversary Edition. This puppy is an unlocked $72 dual-core Haswell that just screams potential. That’s the sort of overclocking a regular dude could get into. We have one on order and will begin abusing it as soon as we can.