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Intel Core i7-7740X Kaby Lake-X Review

Final Analysis

Superficially, Intel’s idea to transplant Kaby Lake onto its high-end desktop platform seems like it'd make sense. But ultimately, X299's excessive cost hamstrings Kaby Lake-X. In many ways, the Core i7-7740X reminds us of Intel’s Core i3-7350K. It's a great chip forced into a platform that doesn't match up with its price point.

Core i7-7740X is nearly identical to the existing -7700K; even its price is similar. At stock settings, the -7740X performs a lot like its mainstream counterpart, despite slightly higher base and Turbo Boost frequencies. We noticed the same performance characteristics as -7700K in lightly threaded workloads, such as gaming and most common desktop apps. But the -7740X pales in comparison to the brawnier Skylake-X models in heavy application tests. Lower idle power consumption numbers are likely a result of the -7740X's disabled graphics engine. However, the overall power and thermal measurements come out to be almost the same. Though we still don’t approve of the thermal paste Intel uses between its die and heat spreader, at least closed-loop liquid coolers are fine for this 112W chip.

The “X” in Kaby Lake-X promises extreme overclocking action, and we did eke out a few hundred megahertz over Core i7-7700K. That extra headroom is nice, but it doesn't translate to large gains in our gaming suite. In fact, at stock settings, the -7700K achieved higher average frame rates, while overclocking gave the -7740X a 1.19% advantage. The 99th percentile variances between the chips both fell under 1%, with the advantage going to Core i7-7700K in stock and overclocked configurations. In either case, the difference between these two CPUs is imperceptible, even after overclocking them both. Perhaps that'll improve as X299-based motherboards receive more fine-tuned firmware.

Intel's Core i7-7700K is one of the fastest gaming processors we've ever tested, so matching it is a good thing. But the -7740X doesn't make sense as an equal when we factor in the X299 platform. You are going to pay an extra ~$150 for an X299 motherboard compared to a more mature Z270-based setup, and gain exactly zero features. In fact, you lose the integrated GPU that could be useful for other tasks, such as Ultra HD Blu-ray playback. Dropping the -7740X into LGA 2066 actually disables motherboard features you're paying for like extra DIMM slots, Skylake-X's more robust power delivery, and hamstrung chipset functionality.

Our motherboard contacts have expressed a general reluctance to create Kaby Lake-X-specific motherboards, and unless that changes, there is little reason to jump up to the X299 with a Kaby Lake-X chip. Certain enthusiasts will pursue a stouter overclock from the Kaby Lake architecture, and -7740X delivers in that regard. Intel's pitch is that Core i7-7740X serves as an entry point to X299 that paves the way for upgrades to Skylake-X later. We don't believe there's a big market for an expensive path like that, though. For those with the upgrade itch, either stay with the Z270 and spend bigger on a high-end GPU, or splurge on a true HEDT-class processor.

Intel has its Coffee Lake CPUs coming to market later this year, and we've heard rumors of a six-core model landing on the mainstream desktop. Consider waiting for more information on that prior to going the X299/Kaby Lake-X route, if you're still interested in Core i7-7740X. Also, AMD's Ryzen Threadripper is coming soon. There are just so many reasons not to buy this thing...

Core i7-7740X doesn’t give you anything new. Yes, it's one of the fastest gaming chips ever made, but you can get similar performance from the mature Z270 platform for significantly less money. We appreciate the higher overclocking ceiling, but that doesn't translate into enough benefit to justify the extra investment.


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Paul Alcorn

Paul Alcorn is the Deputy Managing Editor for Tom's Hardware US. He writes news and reviews on CPUs, storage and enterprise hardware.

  • AgentLozen
    I'm glad that the option for Kaby Lake is available on the x299 chipset. In practice it seems impractical. This article shows you have to pay a lot more for slightly higher overclocking potential.

    I'm curious what Intel's plans are for next year regarding their high end desktop chips. They've already used the Kaby Lake X name for this generation. Should we expect Kaby Lake X 8900X?
  • Kaz_2_
    Intel high power consumption is not great in thr long run. You want the best for your investment
  • TJ Hooker
    The curve below shows clearly that waste heat isn't dissipated quickly enough. Just as we did in our AMD Ryzen and Intel Core i9 launch articles, we used a very thin copper plate to measure the heat spreader's temperatures as well.
    Why aren't there any numbers/divisions on the horizontal axis? Also, you say you did the same thing for the Ryzen reviews but I didn't see a similar graph in those articles (might just be blind though).
  • keith12
    in the HPC graph, you have two 'Ryzen 7 1600x' s.....
  • keith12
    power consumption gaming loop - I5 7600x?
  • the nerd 389
    How does the thermal performance of this chip compare to the 7700k? Specifically, does the larger surface area of the heat spreader give you a meaningful increase in thermal conductivity between the die and the heatsink?
  • rantoc
    Dang intel seem to be doing yet another stupid move with X299 beside rushing it out the door making the AMD's pretty brand new architecture/platform appear mature in comparison. As for this move - What's the incentive to pay premium for the X299 when getting a chip like this that won't even utilize it fully? The 7700k and platform are equal in performance in most tests and far cheaper...

    With the poor thermal transfer between the core and heat-spreader the retail chips won't likely even overclock well either. Never cared about the cherry picked "reviews" chips at all when it comes to overclocking as they very rarely represent the retail chips.
  • rantoc
    What's the incentive to buy an expensive motherboard and yet get near zero of it's true potential with this cpu? That's paying for a lot of real estate that can't be used at all and on top of that the same poor thermal transfer between the core and heat-spreader meaning a good stable oc is harder to obtain and far less likely to happen on the retail IE non-review cherry picked ones.

    I think intel shoot themselves in the foot by scaling this one down to much and then couple it with an overpriced platform for what you get out of it, x299 will be good no doubt but only with the right chips and only when the rushed out of door bugs been fixed.
  • This is awesome setup because you can buy x299 motherboard for $219 dollars already which gives you amazing room for later upgrade and this CPU can run 5.0Ghz easily producing very little heat. People at Toms Hardware completely missed the point. I'd rather get $219 x299 motherboard than outdated Z270 for $160.
  • And as for heat...i think heat talk i have been reading lately is just BS.