Intel Core i9-7900X 3.3 GHz Review 99

Intel Core i9-7900X 3.3 GHz Review

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Value and Conclusion

  • The Intel Core i9-7900X retails for $999.
  • Strong single-core performance
  • Beats Threadripper 1950X at multi-threaded media encoding
  • Monolithic quad-channel memory interface, fewer things to configure
  • Plenty of aftermarket cooling solutions
  • High price
  • High idle power draw
  • No ECC memory support
  • Fewer PCIe lanes than Threadripper
Intel made some poor choices in differentiating the lower end of its Core X family, but the Core i9-7900X stands out as a wholesome high-end desktop product at the $1000 mark. The "Kaby Lake-X" quad-core chips are a terrible choice for the uninformed consumer, the i7-7800X and i7-7820X lack the full PCIe connectivity, forcing you to shell out at least $999 on a chip that has it, but by itself, the i9-7900X provides a powerful combination of both single-threaded and multi-threaded performance.

Intel's "Skylake" micro-architecture continues to enjoy higher IPC than AMD's newer "Zen," and it reflects in higher performance than the AMD Ryzen Threadripper 1950X in every less-parallized benchmark, including games. It's only at GPU-limited resolutions, such as 4K Ultra HD, that Threadripper catches up because the GPU is the limiting factor. The 7900X's single-threaded performance, however, isn't higher than that of the mainstream-desktop Core i7-6700K despite the higher L2 cache (refer to "CineBench R15 ST"). The idea behind more L2 cache appears to be more one of reducing latency in inter-core communication than an attempt to improve IPC.

The Core i9-7900X trades blows with both the $799 Threadripper 1920X and the par-priced Threadripper 1950X at multi-threaded tasks. In most synthetic multi-threaded benchmarks, the 1950X is more than comfortably ahead of the i9-7900X due to its six extra cores. On multi-threaded media encoding tests, such as x264 and x265 video-encoding (which is a real-world test where we're feeding a test video to the encoder), the i9-7900X is ahead of the 1950X.

The Core i9-7900X also benefits from a key design advantage "Skylake-X" has over the Ryzen Threadripper in that it's not a multi-chip module and has a monolithic quad-channel memory interface. Data is interleaved over four memory channels, while the Threadripper uses two 8-core "Zeppelin" CPU dies with dual-channel memory interfaces, each (like a 2-socket system). This becomes a problem with the two key usage cases of HEDT processors - gaming and megatasking. With gaming, you need memory to have as little latency as possible, and the game itself isn't very parallelized, so Threadripper features a software toggle called "Game Mode," which localizes memory accesses to modules controlled by one of the two dies for the least latency and also disables half the CPU cores. For megatasking, where you need as many cores and as much memory bandwidth as possible, Threadripper has its primary (and default) mode called "Creator's Mode", which spans memory across all four memory channels and keeps all CPU cores active. Switching between these modes requires a reboot, and Game Mode works worse than Creator's Mode in some games, which adds even more complexity. The monolithic quad-channel memory interface of the i9-7900X is fire-and-forget - all your applications will run at maximum performance.

Overclocking the Core i9-7900X from its 3.30 GHz nominal clock to 4.50 GHz (all cores) on air-cooling wasn't difficult, but that speed is close to the 4.30 GHz boost you already get on "some" of the cores. The Turbo Boost Max 3.0 algorithm works without any user intervention, and again, is an attempt to make sure a high core count doesn't pose performance issues for less-parallized tasks.

If you're purely gaming with a little bit of productivity or game streaming thrown in, this is not the chip for you. The newly launched Core i7-8700K doesn't just have higher gaming performance, but also plenty of multi-threaded performance for a "gaming plus" desktop. You save on not just a cheaper processor, but also a cheaper motherboard. It also comes with much higher clock speeds, which benefits applications such as Photoshop, Excel, and PowerPoint.

If you work with highly threaded apps all day or have full control over the code your software runs, which means it can be hand-optimized, Threadripper could be a good alternative due to offering more cores (= more performance) for the money, but such scenarios are fairly limited. Also, if you do 4K gaming, which will be GPU limited anyway, then Threadripper could be reasonable if you want to keep up with Game Mode switching.

The Core i9-7900X will come through if you want not just high multi-threaded performance for content-creation tasks, but vast platform connectivity options for such things as 4K video-capture cards, Thunderbolt cards, NVMe SSDs, etc., though such comes at a significant cost.
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