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


Intel’s market dominance burdens the company with certain expectations when it launches new hardware. Naturally, we expect more performance. And although we're quick to deride incremental updates, forward progress is what we want to see. At no point is a step backward alright in our books, and we saw a handful of those in today's tests.

Intel's mesh fabric and AMD's Infinity Fabric demonstrate how highly parallel architectures require more sophisticated interconnects. In some cases, they introduce performance regressions compared to simpler configurations that connect subsystems more directly. Remember, both companies used their previous-generation layouts for over a decade, and early implementations weren't without weaknesses that were later improved.

Most recently, Ryzen faced some puzzling performance issues at launch. More than three months later, a steady stream of firmware, chipset, and software updates has rectified a lot of the issues we initially identified. Even in this story, revisiting Ryzen 7 1800X leaves us with a very positive impression, particularly compared to Intel's $1000+ alternatives. Ryzen didn't magically become the fastest CPU out there, but it's impossible to ignore at its price point.

Enthusiasts might hope for similar improvements from Intel. After all, AMD is overcoming its roadblocks with a fraction of the R&D budget. We asked Intel if it expects software-based optimizations to fix what disappointed us, and company representatives responded that software tuning for the new architectural enhancements and cache hierarchy could improve performance. Remember, though, Core i9-7900X is based on the same micro-architecture as older Core CPUs. It's improbable that mere code updates will rectify issues introduced by Skylake-X's layout when Skylake-S and its derivatives are already well-supported.

As it stands, aggressive Turbo Boost frequencies and a re-balanced cache hierarchy go a long way to improving on Broadwell-E's minor weaknesses. When the Core i9-7900X does well, it really shines. Often, the chip beats every competitor we throw up against it, including Core i7-6950X. In other workloads, latency imposed by its mesh topology causes Core i9 to stumble. That isn’t to say performance falls off completely. But we do see anomalies unfitting of a $1000 CPU. If you're strictly a gamer, Core i9-7900X won't make you want to buy a new CPU, motherboard, and memory kit.

Enthusiasts also want to see robust overclocking capabilities, and Skylake-X does offer a higher frequency ceiling than Core i7-6950X. You're going to cope with a lot of heat in the process, though. Given Intel’s insistence on using thermal paste between its die and heat spreader for longer-term reliability, the processor can’t dissipate heat as effectively, so thermal performance becomes a limiting factor. Plan on investing in a beefy open loop if you want to push the Core i9-7900X much further than its stock frequencies.

Core i9-7900X performs well in our productivity, workstation, and HPC tests. The mesh-imposed disparities aren't as pronounced in those benchmarks. But we also have re-run Ryzen 7 1800X benchmarks to think about. Pressure to size up has pushed AMD's flagship down to $460, less than half of what a Core i9-7900X would cost. While Intel may capture the top 1% of high-end enthusiasts with Skylake-X, everyone else has to consider whether Ryzen may be the smarter buy.

Moreover, AMD's upcoming Threadripper CPU has to have Intel worried. How do we know? The X299 motherboards we used needed firmware updates to address very serious performance issues right up until launch. Intel didn't seem nearly as ready for Skylake-X's introduction as we'd expect. A number of Core i9s with even more cores won't be ready until later this year. However, it looks like Intel couldn't get the four-, six-, eight-, and 10-core models out fast enough. They'll ship later this month.

Unfortunately, this story won't be ready to wrap up until we have Threadripper to compare against. Given Core i9-7900X’s high price and performance caveats, enthusiasts should probably hold off on a purchase until we know more about the competition, even if Skylake-X looks like a bigger step forward than Intel's past HEDT designs.


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