Skip to main content

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

Image 1 of 9

Image 2 of 9

Image 3 of 9

Image 4 of 9

Image 5 of 9

Image 6 of 9

Image 7 of 9

Image 8 of 9

Image 9 of 9

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).

Image 1 of 7

Image 2 of 7

Image 3 of 7

Image 4 of 7

Image 5 of 7

Image 6 of 7

Image 7 of 7

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.


MORE: Best CPUs


MORE: Intel & AMD Processor Hierarchy


MORE: All CPU Content

  • 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!
    Reply
  • 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!
    Reply
  • James Mason
    So it seems like de-lidding the x299 processors is gonna be a standard thing now to replace the TIM?
    Reply
  • 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.
    Reply
  • prophet001
    There's obviously a problem if the delta is that high.
    Reply
  • James Mason
    19835717 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.
    Reply
  • 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!!
    Reply
  • James Mason
    19835862 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 availableGenerated by PCPartPicker 2017-06-19 10:47 EDT-0400
    Depends on which watercooler and which ram, but not really.
    Reply
  • 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.
    Reply
  • 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?
    Reply