Intel Core i9-7900X And Core i7-7740X CPU Review: Skylake-X and Kaby Lake-X Debut

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Introducing The Intel Core X Series Processors

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Over the next few months, Intel will be releasing an array of new high-end desktop processors in the recently-announced Core X Series, based on the Skylake-X and Kaby Lake-X micro-architectures. The first chips in the series to arrive in the lab are the 10-core Core i9-7900X and quad-core Core i7-7740X. We’ve got an array of benchmarks and overclocking data on tap with the processors, but due to some unexpected shipping issues, we weren't able to complete all of the test we would have liked. Rest assured, we’ll update this piece as soon as we can with a full set of numbers -- it will just take a few days.


In any case, the Core i9-7900X will be the first of the high-end chips to arrive and it will supplant the 10-core Core i7-6950X at the top of Intel’s desktop processor line-up. It’s an expensive proposition, but due to increased pressure from AMD with its Ryzen 7 and upcoming ThreadRipper processors, the Core i9-7900X will be roughly half of the price of Core i7-6950X.
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The entire family of upcoming Core X-series processors is outlined in the chart below. Intel is claiming that these chips are the company’s “Most Powerful, Most Scalable” desktop processors to date, which seems fitting since they scale from a quad-core part with only 16 PCI Express lanes all the way on up to a monster 18-core chip with an expected 44 lanes (though that hasn't been confirmed just yet).

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Intel Core X-Series Processor Line-Up - Starting @ $242

The Core i9-7980XE (Extreme Edition) sits atop the new line-up. This beast is packing 18 Skylake cores (36 threads with HyperThreading) and has a TDP of 160W – though frequencies haven’t been revealed just yet. In addition, the entire Core i9 family has support for a more refined version of Turbo Boost Max 3.0 (more on this on the next age), quad-channel DDR4-2666 memory, and Intel Optane (3D XPoint) memory technology when used on compatible motherboards (which should be just about all of them).

Many thought that AMD would have the core count battle won this generation with its upcoming 16-core/32-thread Ryzen Threadripper processor, but Intel put the kibosh on that with the Core i9-7980XE. When the processors finally ship, the Ryzen Threadripper 1998X will be going head-to-head with the slightly "lower-end" Core i9-7960X, which also features 16 cores and support for 32 threads. However, AMD could undercut Intel on pricing, as they've done with previous Ryzen SKUs.

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Along with the Core i9-7980XE, there are four other members of the Core i9 family coming, including the Core i9-7960X, i9-7940X, i9-7920X, and i9-7900X which have 16, 14, 12, and 10 cores, respectively. Of all the Core i9 processors announced, Intel has only provided clock speeds for the Core i9-7900X, which also happens to be one of the chips we’ll be showing you here today. The Core i9-7900X has 13.75MB of L3 cache, a base clock of 3.3GHz, a Turbo Boost frequency of 4.3GHz and Turbo Boost Max 3.0 frequency of 4.5GHz.

Skylake X CPUZ  Skylake X CPUZ cache
Intel Core i9-7900X CPU-Z Details

Working our way down the stack, there are two Skylake-X-based Core i7 models, although only the Core i7-7820X (priced at $599) supports Turbo Boost Max 3.0. That processor has eight cores/16 threads, a base clock of 3.6GHz, a Turbo Boost clock of 4.3GHz, and Turbo Boost Max 3.0 of 4.5GHz. It features 11MB of L3 cache, 28 PCIe Gen 3.0 lanes, and has a TDP of 140W. The Core i7-7800X drops down to six cores/12 threads and has quad-channel memory support at DDR4-2400 speeds.

Kaby Lake X CPUZ  Kaby Lake X CPUZ Cache
Intel Core i7-7740X CPU-Z Details

We should mention that of the nine new X-Series processors coming down the pipeline, only seven of them are based on the Skylake-X architecture. The remainders are based on Kaby Lake-X. The two Kaby Lake-X-based processors, also happen to be the least powerful of the bunch. The Core i7-7740X has four cores/eight threads along with base/Turbo Boost 2.0 clocks of 4.3GHz and 4.5GHz respectively. With a base clock of 4GHz and Turbo Boost 2.0 frequency of 4.2GHz, the Core i5-7640X has just four cores (four threads) and 6MB L3 cache. Both of the chips support dual-channel DDR4-2666 memory and have 16 PCIe Gen 3.0 lanes.
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Skylake-X (Top), Kaby Lake-X (Bottom)

Also note that all of these processors are fully-unlocked for easier overclocking and the platform has full support for related overclocking features like Extreme Memory Profile (XMP) 2.0 technology, memory controller trim voltage control, PEG/DMI overclocking, and per-core overclocking/voltage.

As you can see in the chart further up the page, pricing is all over the map, with the entry level Core i5 arriving at $242 and the flagship 18-core Core i9-7980XE commanding a hefty $1,999. The Core i7-7900X and Core i7-7740X we’ll be showing you here are priced at $999 and $339, which is somewhat refreshing. The 10-core Core i7-7900X – though faster – is “only” half the price of the previous-gen 10-core Core 17-6950X and the Core i7-7740X is right in-line with the Core i7-7770K, which has similar specifications.

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