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Intel Core i9-7900X ‘Skylake-X’ 10C20T CPU Indepth Analysis

The Intel Core i9-7900X ‘Skylake-X’ 10-core processor unlocks a new level of performance for enthusiast consumers. Multi-threaded performance is superb thanks to the use of ten physical cores with Hyper-Threading and quad-channel memory, while lightly-threaded results are equally promising thanks to the high clock speeds used in tandem with Intel’s excellent Skylake architecture.

Multi-threaded performance from the i9-7900X is at a whole new level. Performance increases over the Core i7-6950X in Cinebench, Handbrake, 7-Zip, and x265 encoding are in double-digit figures in percentage terms before overclocking is thrown into the mix. Skylake-X’s current flagship is the fastest consumer processor available for a variety of multi-threaded tasks. It’s quite the bargain compared to the ridiculously-priced i7-6950X, too, not that that is any form of praise.

Gaming performance is good but it’s not market-leading. Users interested solely in gaming (not streaming) should be looking at the Core i7-7700K for their system. There are, however, several results which place the Broadwell-E i7-6950X in front of the i9-7900X in gaming performance. This is likely due to the rebalanced cache configuration of the CPU (though a lack of early software optimisations is also likely to be playing a role).

That’s disappointing for many users who, justifiably, would have expected superb multi-threaded performance from the i9’s 20 threads and near chart-topping gaming performance thanks to the use of high-speed Skylake cores.

Then we move onto the sticky points for the current Skylake-X flagship – overclocking, thermals, and power consumption.

Starting first with overclocking, the results are generally good for a 10-core HEDT CPU. We hit 4.6GHz at 1.20V and expect than many chips should be fine at a similar frequency on all cores. In isolation, this would be a solid outcome. However, the fact that our overclocking results were temperature-limited was disappointing.

Intel’s thermal design for the Core i9-7900X is not good. The use of TIM on a power-hungry 10-core CPU results in undesirable temperature levels at stock speeds and readings that easily push towards 100°C under reasonable overclocked voltage levels without using the best CPU cooling available off-the-shelf. If you want to hit the aforementioned 4.6GHz at 1.20V, you’ll have to cross your fingers and hope for low ambients when using an air cooler or put up with incredible fan noise from a hard-pushed AIO.

The use of solder or some metal under the heatsink would have solved this issue and the associated costs would be easily absorbed into a $999 retail price. Instead, Intel has chosen to opt for the cheaper route of using barely satisfactory TIM that will force users to invest, perhaps unnecessarily so, in higher-quality cooling hardware and run their system at higher (louder) fan speeds. Hardly the mark of quality that one would expect from such a premium processor on such a premium platform. De-lidding is an option but on a $999 processor, it is certainly not a procedure that I would feel comfortable undertaking with my own two hands.

Probably unsurprising, given the lofty temperatures, power consumption for the Core i9-7900X is very high. Out-of-the-box, the CPU draws more power than any other stock-clocked processor we compared it to, with only the overclocked Core i7-6950X commanding more energy. Dial in a reasonable overclock to 4.6GHz with 1.20V and system-wide power draw will easily hit 400W under rendering load.

It is evidently difficult to analyse the Core i9-7900X. On one side of the argument, Intel has delivered ground-breaking performance to a consumer market at a significant price reduction from the previous generation, all tied together within the feature-heavy X299 chipset. However, thermal performance is poor, power consumption is very high, and gaming performance is rarely near first place.

With the Core i9-7900X, Intel has used the brute force approach to countering AMD’s Ryzen 7 and pre-emptively striking against Ryzen Threadripper. In doing so, finesse has gone out of the window and the staple characteristics that have long been associated with Intel processors – power efficiency and decent thermal performance – have quickly followed. Core i9-7900X is a solid option if you must have the best of the best and have tasks that warrant the significant investment. Just do not expect to feel all warm and fuzzy like you would had you invested in a well-polished, no compromise, price-efficient platform.

We wait eagerly to see what AMD’s Ryzen Threadripper brings to the table in just a few weeks, and would advise potential buyers of Core i9-7900X to do the same.


The Intel Core i9-7900X is available for £949.99 (at the time of writing) from Overclockers UK.

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  • Superb out-of-the-box multi-threaded performance.
  • Strong lightly-threaded performance thanks to Turbo Boost 2.0 and Turbo Boost Max 3.0.
  • High all-core frequencies when overclocked, provided you can cool the chip.
  • 44 PCIe lanes will appeal to multi-GPU users.
  • Strong memory potential – high-speed, quad-channel, up to 128GB.
  • X299 chipset feature set is a significant improvement over X99.


  • Thermal performance is poor.
  • Power consumption is very high.
  • Extremely expensive and questionable value compared to AMD’s Ryzen 7 offerings.
  • Gaming performance in some titles not as strong as Kaby Lake or Broadwell-E.

KitGuru says: A brute force approach that has the finesse of a bulldozer smashing through performance barriers. Intel’s Core i9-7900X is, overall, the fastest consumer processor on the planet and can overclock to impressive speeds for a 10-core chip. Just make sure you do not expect reasonable thermal performance, low power consumption… or much change out of £1000.

Rating: 7.5.

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  • Syed Muhammad Sanabil

    Good review . Honestly even if Intel gets all the goodness of being a fast processor its highly priced. Also poor thermal performance is a big deal because processor eventually runs hot and performance will take a toll.
    I am personally waiting for Threadripper AMD’s line up to compete with Intel’s half cooked CPU.If AMD TH has good price and good thermal efficiency then even if it is a bit slower then Intel’s offering people will go for it. Ryzen 7 and especially Ryzen 5 1600 cpu proved this already

  • Dennis Achterberg

    What about VRM temperatures? 🙂

  • Lelisevis

    This is a review of the CPU. The VRM temps are going to vary depending on the board and its overly extravagant but largely useless cooling shroud.

  • vasras

    Brilliant and thorough review, thank you very much.

    I’d be happy with quad memory-channel i7-7740X with 44 PCI-e lanes. Fast enough for _everything_ I need, and would have enough memory and PCI-express bandwidth for the workloads I run (don’t need 10c/20t).

    Unfortunately, it doesn’t exist. Either I have to buy the crippled i7-7740x with 28 PCIe and dual channel memory OR I have to buy the over-priced space heater that is the 7900X with a motherboard that fries eggs with the VRMs and sucks so much electricity out of the socket that I can hear the kill-o-watt whirr like crazy in the background while notes keep flying out of my wallet.

    No thanks Intel. You really outdid yourself this time around.

    I will wait for the ThreadRipper from AMD.

  • Michał Kubiak

    I like your test, but let me make a small correction, 7900X is faster then Ryzen only because of more cores and higher clock, not due to “modern architecture” (which while newer? then Ryzen is by no means better). But to count my chickens 🙂 Ryzen_OC is 4.05Ghz, 7900X_OC is 4.6Ghz
    1776*1.25(because Intel has 25% more cores then AMD)=2220
    now to equalize core speeds: 2220*4.6/4.05=2521 (the Ryzen score as it would be at 4.6Ghz) – IPC wise Intel (scored 2449) is still a bit worse then AMD in Cinebench.
    I’m not saying that AMD is better since it can’t at the moment reach 4.6Ghz nor does it have 10 core CPU to fight with.
    Similar thing happens with x265 encoding benchmark: 30,6*1,25*4,6/4,05=43,4444444 – a bit faster then Intel. And it is all in tasks that put use to AVX2 and there is still Intel advantage in 4 channel memory.

  • Michał Kubiak

    Well, at least you can wait a bit and see if Threadripper is actually better then Intel – there is no guarantee it is. Especially for lightly threaded tasks that you speak of (that per chance require high core clock that will most likely not be reachable on TR).

  • AMDs single core IPC is slightly worse than Intels, but AMDs implementation of SMT vs Intels HT brings it out on top by a slight margin at the same core/clocks in multi threaded benchmarks while losing in the single core benches. And then AMD doesn’t really OC well, neither does memory clock up well, its improving of course but not at any great pace.

  • roadkill612

    Bottom line w/ Ryzen is mem clocks pf 2933 are a no brainer, and known to work 3200 components are common.

    Thats the consensus on the street.

  • roadkill612

    A pact with the devil will always bite u in the ass.

    How can u trust intel?

    Buy a $999 cpu w/ scads of lanes, & discover there is an charge to use nvmeS as they should be. Slimy.

    The new keying system shows they use their research dollars to effect better ways of screwing customers. A good look guys.

    I would buy amd gear if same money and 10% worse. My time, upgradeability, conscience and dignity are worth something too, thanks intel.

    AMD probably are 10% worse in the criteria intel like to use, but AMDs modular/fabric architecture, is miles better than intel has or will have achitecture, for future cost effective ~equivalent outcomes.

    BTW the prices u list for amd dont reflect reality. Both are much cheaper on amazon etc. Further, the widely regarded sweet spot is the 12 thread r5 1600, at ~$220

    Lanes are just sufficient on ryzen, for a 16 lane gpu, a 4 lane nvme ssd onboard and a 4 lane pcie2 nvme ssd (~1.6GBps, or triple a sata ssd).. Beyond that, u have stacks of sata and .5GBps pcie2 expandability, but no 1GBps pcie3 lanes

    note also, amd pcie3 lanes are direct to the cpu, not via switches and bridges like most intels.

  • Christopher Lennon

    Newsflash, the i7-7740X only has 16 PCIe Lanes, not 28!

  • Javier Saove

    Test w/ agesa 1006 please…..

  • 1011101001001

    Not sure why you would complain about a crippled quad core and decide to wait for a 10 core minimum threadripper lol. Amd has some amazing stuff coming out, but it will not have the IPC of intel.
    The 8 core intel is actually a pretty sweet chip. It can overclock 2 of its best cores to 4.5 ghz for single or two thread tasks and 4.3 turbo on all cores. The thermal is only an issue when overclocking and when you get this many cores it will always be a problem when overclocking. Amd hasnt been able to go over 4.1 ghz yet.

  • janon

    Intel PCIE lanes are direct to the cpu as well. And if intel says a cpu has 16 lanes (like the 7700k) then those are dedicated to the GPU. The rest, in that case, come from the chipset via dmi 3. This is unlike AMD who is currently *overstating* PCIE lanes available for video. Sorry to burst your fanboy delusion bubble

  • janon

    I strongly suspect nothing you do requires 44 PCIE lanes or quad channel RAM. People complaining
    about 7900x, and somehow not satisfied with *either* Kaby Lake *or* Ryzen 5/7, and obsessing instead over “Thread Ripper” sound generally clueless.

    AMDs marketing is really working for TR. Somehow every hump on comment threads is now convinced they’re doing all sorts of things that somehow justify *32 threads*, even at lower IPC, and *dozens* of PCIE lanes and *mountains* of memory bandwidth. Enormously unlikely.

  • Çağan Çelik

    You can’t run a 32GB kit @3200Mhz on Threadripper cpu, it just fails to boot. Worst memory controller ever on a cpu i guess. It maxes out @ around 2800Mhz if you install 32gb of ram. If you go higher like 64gb, then you end up with 2133Mhz ddr4 speeds or 2400 if you are lucky.

    Whereas I am running 64GB 3800Mhz CL15 kit with my 4.8Ghz 7900X. Unleashes my 2x overclocked Titan Xps in SLI. AMD doesn’t clock well, has the worst memory support and has lower IPC and thus lower gaming performance. It’s just good for rendering & encoding farms.