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Entering Devil's Canyon: Does the Intel Core i7-4790K Do 5GHz?

Reviews of Intel’s Devil’s Canyon processors have been trickling out into the wild after their doorbusting appearance at Computex and unfortunately, the news hasn’t been as good as Intel made it out to be. We have samples of the Core i7-4790K and Core i5-4690K in house, with Pentium Anniversary Edition chips en route. I haven’t had a chance to play with the i5-4690K yet, but I’ve put some mileage on both i7-4790K chips.

If you’ll recall, the original Haswell i7-4770K developed a fairly unhappy reputation in enthusiast circles as a hot, inconsistent overclocker. I’ve tested three retail chips and two ES chips; the retail chips would top out at around 4.3GHz while the two ES chips were able to do 4.5GHz. In either case, I hit both clock and heat walls where a tenth of a volt was required to hit the next multiplier, and the chip was already peaking at 90C on the cores under water. Running the i7-4770K past 1.25V was asking for trouble.

Same stepping, same revision, but a change of package and possibly better binning helps Haswell be the overclocker it should've been from the start.

Devil’s Canyon, on the other hand, seemed exciting right from the specs. While vanilla Haswell was having trouble going to 4.4GHz and beyond in the wild, the i7-4790K was specced to hit 4.4GHz on a single core right out of the box. Intel promised changes to Haswell that would improve overclocking potential, but those really just boil down to a change in thermal interface material beneath the heatspreader and some extra capacitors on the underside of the chip to smooth power delivery. The i7-4790K isn’t even a new stepping; we’re still C0 just like we were with Haswell.

Internal testing mirrors experiences reviewers have had with the Core i7-4790K. Both of our samples hit 4.7GHz at 1.3V, which is about as high as you’d want to push through the chip for regular use. Intel seems to be a victim of their own hype; Intel was telling everyone they’d be doing 5GHz on air, but that hasn’t been repeated by any members of the press. Both of my samples are under water; one under a custom loop, the other under an H110.

While the i7-4770K had issues with heat transfer, the i7-4790K will allow your cooling system to stretch its legs.

That said, Haswell’s thermals are vastly improved with the Core i7-4790K. Tom’s Hardware measured the new thermal interface material as buying you about 7C; my experience is actually more optimistic. Devil’s Canyon removes Haswell’s heat wall; your primary limitation now is the silicon and not heat. OCCT testing at 4.7GHz and 1.3V has cores peaking in the low 80s and spending most of their time around 70C, which is a massive improvement over vanilla Haswell. Interestingly, though, the IMC on one of the samples has a hard time going past DDR3-2666, even at stock clocks. I was planning on investigating memory and Devil’s Canyon at some point down the line, so we’ll revisit this.

If Intel hadn’t promised us the moon we might be a lot happier with the i7-4790K. A fairly reliable 4.7GHz at least lifts the performance ceiling for overclockers, a ceiling that hasn’t moved since Sandy Bridge. Again, though, these are engineering samples. Retail chips could actually go either way; anecdotally, my ES 4770Ks were consistently better than the retail ones I tested. As retail 4790Ks trickle out, we should be able to see about where these chips are going to land.

For now, the 4790K isn’t a clear upgrade over the 4770K or even the 3770K or 2600K/2700K. If you want a new toy to play with, it’s here, but the rest of us might want to hold our breath for Haswell-E.


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