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

Caching Up & IPC, AVX, Cryptographics

For Skylake-X, Intel shrunk Skylake-S' shared last-level cache and transitioned from an inclusive to a non-inclusive scheme. Efficient caching algorithms that maximize the L2 cache hit rate are a key component of this change. The 'rebalancing' reduces per-core L3 cache to 1.375MB; further, Intel modified it to operate as a victim cache that fills with data evicted from the private L2 cache.

Intel also quadrupled each core's L2 cache from 256KB to 1MB. More lower-latency storage space should have a positive effect on performance, though Intel hasn't said how it implemented the silicon-level changes to its Skylake architecture.

Cache & Memory Latency And Bandwidth

Of course, the mesh's latency and bandwidth have an impact on cache and memory throughput, so we conducted a series of tests to compare our contenders, again using SiSoftware Sandra.

We did spot slightly higher L2 latency from Core i9-7900X compared to Core i7-6950X during the in-page random test, but Skylake-X's L2 latency dropped below Broadwell-E during the sequential access pattern. The multi-threaded cache bandwidth test reported a large performance advantage favoring Core i9-7900X.

IPC, AVX, Cryptographics

Due to limited time with Skylake-X ahead of its launch, we ran a preliminary set of IPC-oriented benchmarks. It's possible that further optimizations, or a more expansive set of workloads, might return different results, but we'll be sussing that out in the days to come.

We set a static 3 GHz clock rate for the following tests. It's important to note that Intel didn't specifically call out increased IPC as the source of its 15% single-threaded and 10% multi-threaded performance gains over Broadwell-E. Instead, the company based its claims on a comparison to Core i7-6950X with pre-silicon Spec*int_rate_base2006 tests (subject to a +/- 5% margin of error).

The single-threaded Cinebench test doesn't show a performance difference between Skylake-X and Skylake-S. However, there is a 1.54% improvement over Broadwell-E. The Ryzen processors clearly don't get as much done per clock cycle, and both trail.

Switching to the multi-threaded Cinebench benchmark exposes a larger difference between Intel's 10-core contenders and the rest of our pool. Core i9-7900X and Core i7-6950X remain the focus, though: we record a 1.93% delta between them.

Core i9-7900X employs two 256-bit AVX FMA units per core that operate in parallel, whereas Ryzen's Zen architecture divides 256-bit AVX operations across two FMA units per core. Intel deactivates one FMA per core on the sub-10-core Skylake-X models. As such, Core i9-7900K has an inherent advantage in the y-cruncher benchmark, a single- and multi-threaded program that computes Pi using AVX instructions. We tested with version 0.7.2.9469, which includes Ryzen optimizations.

The -7900X's single-core SHA2-256 test results are nearly twice that of the two previous-generation models due to Intel's targeted AVX2 optimizations for hashing performance. That same advantage carries over to the threaded test. Intel offers AVX-512 support with the Skylake-X processors but doesn't employ all 11 features in the desktop models. Instead, the company targets specific feature sets at different market segments.

The Zen architecture includes two AES cryptographic accelerators for each core, so it isn't surprising to see Ryzen dominate the single-core AES-256-ECB tests. Intel's processors leverage their core count advantage to turn the tables in the threaded AES workload.

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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