Intel Core i9-7900X Review: Meet Skylake-X

Power Consumption & Overclocking

Intel isn't using a soldered integrated heat spreader (IHS) for Skylake-X and Kaby Lake-X. Instead of the metallic solder most enthusiasts want to see, heat moves from the die to the IHS through inexpensive thermal interface material, which is just a fancy name for common thermal paste. This decision has implications for both our power consumption measurements and overclocking efforts.

First, we had to use our industrial-grade Alphacool Eiszeit Chiller 2000 cooler to achieve meaningful test results. Air cooling is out of the question for Core i9-7900X, and even a decent all-in-one liquid cooling solution won’t get far.

Power consumption is measured after the voltage converters and CPU, using points on the motherboard. The 230A we saw during our overclocking tests prompted us to add a fan to the motherboard. We only had one platform for this story, so we played it safe with extra cooling around the LGA interface.

Power Consumption

These numbers are generated using stock motherboard settings; any significant under-volting had no effect, except to cause stability problems.

At idle, the Core i9-7900X comes in below its predecessor and AMD’s Ryzen models. Getting there required a firmware update to correct problems with P-states, among other issues plaguing this platform right up until launch.

Even lightly threaded workloads like AutoCAD 2015, which uses just a few of the Core i9-7900X’s cores, catapult Intel’s -7900X to the back of the pack in power consumption metrics.

This is almost certainly due to higher clock rates than previous-gen HEDT CPUs like the Core i7-6950X. Taking into account Skylake-X's increased performance, though, the Core i9-7900X remains a more efficient solution. One percent more power consumption gets you 29 percent more 2D performance and a massive 39 percent more 3D performance. Both tasks profit from Turbo Boost Max Technology 3.0 in a big way.

If more than three cores are used, the Core i9-7900X’s advantage shrinks considerably. It still beats the Core i7-6950X by approximately 17 percent, but the power consumption increase is a lot larger (around 10 percent).

Pushing all of the Core i9-7900X’s cores with Prime95 or LuxRender propels power consumption to incredible heights. You do get 48 percent more rendering performance in LuxRender, but at the expense of 58 percent-higher power use. This approach has the elegance of a sledgehammer. Then again, if you need speed at any cost, Core i9-7900X is top-notch.

Overclocking and Stability

We now know that the Core i9-7900X’s performance to power consumption ratio turns negative as you utilize more of its on-die resources. Of course, this has to be factored into your overclocking plans, since many coolers can't cope with the heat dissipated by a >200W processor.

Stable overclocking, defined as reliable operation under Prime95 for prolonged periods of time without hitting a temperature limit, wasn’t possible beyond 4.4 GHz. Reports of >5 GHz with all cores active should be taken with a grain of salt. We did boot into Windows at 5.1 GHz, but running actual applications resulted in either a BSOD or a motherboard emergency shutdown.

We did manage to achieve a stable 4.8 GHz overclock under the single- and multi-core Cinebench R15 benchmarks. However, our cooling solution was probably the decisive factor there. Realistically, 4.5 GHz should be achievable with an all-in-one liquid cooler. Let’s take a look at the comparison curves for Cinebench R15 with all cores active:

At a Vcore of 1.4V, the system stayed stable for 10 benchmark runs. Intel's Core i9-7900X consumed an average of 261W, while individual peaks jumped as high as 293W. A test at 4.8 GHz using 20 instances of a year-long shading computation for a rooftop photovoltaic array, including profit calculation, pushed power consumption all the way to 335W. The motherboard shut down after we started Prime95 without limiting AVX. The last recorded value was 364W.

The performance and power consumption curves yield some interesting findings. Performance scales with clock rate in an almost linear fashion. Power consumption increases faster, but not as rapidly as we feared that it might.

The more pronounced curve is due to relatively high values at lower frequencies, where the “background noise” (load caused by other system components) is more noticeable.

So, what’s the final verdict on overclocking Intel's Core i9-7900X? It depends on the quality of your cooler and its ability to move heat off the CPU as quickly as possible.

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145 comments
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    Top Comments
  • Anonymous
    Pros: 10/20 cost now $999
    Cons: Everything else

    My biggest problem with this Intel lineup is that if you want 44 PCIe you have to pay $999. No, thanks. My money goes to AMD ThreadRipper.

    Good review!
    31
  • Jakko_
    Wow, compared to the Ryzen 1800X, the Intel Core i9-7900X:

    is about 25-30% faster
    costs 105% more
    uses 35-40% more power

    Ryzen looks really good here, and together with the temperature problems, Intel seems to be in some deep shit.
    30
  • HardwareExtreme
    Too little, too late. Does Intel really think that just because it has "Intel" written on it that it must be worth $200-$300 than AMD?
    18
  • Other Comments
  • Anonymous
    Pros: 10/20 cost now $999
    Cons: Everything else

    My biggest problem with this Intel lineup is that if you want 44 PCIe you have to pay $999. No, thanks. My money goes to AMD ThreadRipper.

    Good review!
    31
  • rantoc
    Doubt many who purchase such high end cpu for gaming runs at a low full hd 1080p resolution, i know its more cpu taxing to run lower res at higher fps but that's for the sake of benchmarking the cpu itself.

    I would like to see 1440p + 2160p resolutions on a suitable high end card (1080ti or equalent) benchmarked with the cpu as well as it would represent real scenarios for the peeps considering such cpu.

    Thanks for a good review!
    6
  • James Mason
    So it seems like de-lidding the x299 processors is gonna be a standard thing now to replace the TIM?
    4
  • elbert
    Meet netburst 2.0 that not only can hit 100c at only (4.7Ghz)1.2v on good water cooler but only barely beats a 7700k not overclocked in games. All this is yours for the low low price of 3X. Its slower than the old 6950x in a few tests with was odd.
    9
  • prophet001
    There's obviously a problem if the delta is that high.
    1
  • James Mason
    Anonymous said:
    Doubt many who purchase such high end cpu for gaming runs at a low full hd 1080p resolution, i know its more cpu taxing to run lower res at higher fps but that's for the sake of benchmarking the cpu itself.

    I would like to see 1440p + 2160p resolutions on a suitable high end card (1080ti or equalent) benchmarked with the cpu as well as it would represent real scenarios for the peeps considering such cpu.

    Thanks for a good review!

    The differences would be less noticeable at higher res than 1080p, so.... you'd just see less dissimilar numbers.
    1
  • Dawg__Cester
    Hmmmmm. I bought a Ryzen 1700, a water cooler, Asrock B350 MB, 16gb ram 3200Mhz for $590 plus tax. I live in New Jersey. I was very nervous about making the purchase as I knew this was coming out this week but the sale prices got me. Unless you all think I got ripped off, (DON'T TELL ME). But in all honesty I have not regretted the purchase one bit!! I even managed to save enough to get a GTX 1080 FE GPU. I did have a few bumps in the road getting the system stable (about 3 hours configuring after assembly) but I am VERY happy. I used Intel primarily and never really considered AMD other than for Video adapters and SSDs.
    After reading this along with other articles and YT videos, I have no regerts as I enjoy my Milky Way and play my games among other things.
    Just my experience. I am not seeking positive reinforcement nor advice.
    I just feel very satisfied that I did not wait and cough up 3oo more fore something I could have for less. I know, I know it makes no sense.
    But come on fellas, its the computer game!!
    10
  • James Mason
    Anonymous said:
    Hmmmmm. I bought a Ryzen 1700, a water cooler, Asrock B350 MB, 16gb ram 3200Mhz for $590 plus tax. I live in New Jersey. I was very nervous about making the purchase as I knew this was coming out this week but the sale prices got me. Unless you all think I got ripped off, (DON'T TELL ME). But in all honesty I have not regretted the purchase one bit!! I even managed to save enough to get a GTX 1080 FE GPU. I did have a few bumps in the road getting the system stable (about 3 hours configuring after assembly) but I am VERY happy. I used Intel primarily and never really considered AMD other than for Video adapters and SSDs.
    After reading this along with other articles and YT videos, I have no regerts as I enjoy my Milky Way and play my games among other things.
    Just my experience. I am not seeking positive reinforcement nor advice.
    I just feel very satisfied that I did not wait and cough up 3oo more fore something I could have for less. I know, I know it makes no sense.
    But come on fellas, its the computer game!!


    PCPartPicker part list / Price breakdown by merchant

    CPU: AMD - Ryzen 7 1700 3.0GHz 8-Core Processor ($299.39 @ SuperBiiz)
    Motherboard: ASRock - AB350M Micro ATX AM4 Motherboard ($65.98 @ Newegg)
    Memory: G.Skill - Ripjaws V Series 16GB (2 x 8GB) DDR4-3200 Memory ($124.99 @ Newegg)
    Total: $490.36
    Prices include shipping, taxes, and discounts when available
    Generated by PCPartPicker 2017-06-19 10:47 EDT-0400

    Depends on which watercooler and which ram, but not really.
    0
  • Jakko_
    Wow, compared to the Ryzen 1800X, the Intel Core i9-7900X:

    is about 25-30% faster
    costs 105% more
    uses 35-40% more power

    Ryzen looks really good here, and together with the temperature problems, Intel seems to be in some deep shit.
    30
  • HardwareExtreme
    Too little, too late. Does Intel really think that just because it has "Intel" written on it that it must be worth $200-$300 than AMD?
    18
  • vasras
    With these results and crippling by Intel, I think I can wait another 2 months for the ThreadRipper.
    Thank goodness for competition.
    11
  • logainofhades
    Still would buy a Ryzen 1700, and overclock it, over this. The 7900x might be faster, but not enough to justify the higher price tag. I personally think the i9 was a knee jerk reaction to threadripper.
    15
  • the nerd 389
    Is there any way you could investigate the performance of AVX-512 on that CPU?

    The thermal paste has me worried that they won't be able to deliver significant gains over last year's models in that department.
    2
  • MaximusOptimus
    Why are you only using DX11 and 1080P. I would like to see 1440p and 4k game paly
    -1
  • logainofhades
    Anonymous said:
    Why are you only using DX11 and 1080P. I would like to see 1440p and 4k game paly


    Lower resolutions put more of a load on the CPU.
    9
  • Dawg__Cester
    Anonymous said:
    Anonymous said:
    Hmmmmm. I bought a Ryzen 1700, a water cooler, Asrock B350 MB, 16gb ram 3200Mhz for $590 plus tax. I live in New Jersey. I was very nervous about making the purchase as I knew this was coming out this week but the sale prices got me. Unless you all think I got ripped off, (DON'T TELL ME). But in all honesty I have not regretted the purchase one bit!! I even managed to save enough to get a GTX 1080 FE GPU. I did have a few bumps in the road getting the system stable (about 3 hours configuring after assembly) but I am VERY happy. I used Intel primarily and never really considered AMD other than for Video adapters and SSDs.
    After reading this along with other articles and YT videos, I have no regerts as I enjoy my Milky Way and play my games among other things.
    Just my experience. I am not seeking positive reinforcement nor advice.
    I just feel very satisfied that I did not wait and cough up 3oo more fore something I could have for less. I know, I know it makes no sense.
    But come on fellas, its the computer game!!


    PCPartPicker part list / Price breakdown by merchant

    CPU: AMD - Ryzen 7 1700 3.0GHz 8-Core Processor ($299.39 @ SuperBiiz)
    Motherboard: ASRock - AB350M Micro ATX AM4 Motherboard ($65.98 @ Newegg)
    Memory: G.Skill - Ripjaws V Series 16GB (2 x 8GB) DDR4-3200 Memory ($124.99 @ Newegg)
    Total: $490.36
    Prices include shipping, taxes, and discounts when available
    Generated by PCPartPicker 2017-06-19 10:47 EDT-0400

    Depends on which watercooler and which ram, but not really.


    Like I said, I wasn't looking for positive reinforcement or validation as I am more than happy with my set up. But thank you for checking.
    4
  • Randall_Lind
    Why an i5? I thought this was i7 only.
    0
  • dusty13
    well ... at least for 1000 bucks you now not only get a fairly powerful cpu but also a heater for the winter / grill in the summer ... and that just with the standard 10 core model.

    imagine the potential of the obviously unplanned and hastily shoehorned in 12-18core models once they come out in 2018 ... your rig will go nova ^^
    13
  • AgentLozen
    LogainofHades said:

    Lower resolutions put more of a load on the CPU.


    I agree. Imagine if you ran Grand Theft Auto 5 in 640x480 mode. Your graphics card would barely have any work to do. All that's left is whatever the game asks from the CPU. That's when you see which CPU shines brightest.

    Regarding the 7900x, I'm glad to see that Intel responded so quickly to Ryzen. It's too late in the development cycle to make Skylake-X a Ryzen killer, so what we get to see is what Intel had planned for us before AMD made it's comeback.

    The article isn't very flattering toward Skylake-X but it's a much better deal than Broadwell was a year ago. Mostly higher performance at a lower price point. Good for Intel! Good for competition. Still, if I were building a PC right now I might go Ryzen.
    1
  • RanKing7
    "Still would buy a Ryzen 1700, and overclock it, over this. The 7900x might be faster, but not enough to justify the higher price tag. I personally think the i9 was a knee jerk reaction to threadripper."

    You're wrong. I don't even think you understand how processors are made. No company just says "they released that?! Quick make a 10 core processor".

    If 30% increase in performance isn't enough to justify the price tag -- than the processor was never for you to begin with. Neither is Threadripper. These processors are not for budget builds or for feeling the need to justify your decisions to save money. They are for a specific market that is very little of Intel's bottom line.
    -8