Intel Core i9 7900X Skylake-X & Core i7 7740X Kaby Lake-X review: rushed release raises the bar

Intel reinforces lead and introduces most unnecessary CPU ever

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Models

Today, Intel releases five CPUs in total; three Skylake-X and two Kaby Lake-X models.

All CPUs use Socket 2066 and have a model number that ends in an X. As such, Intel calls the combination of Skylake-X and Kaby Lake-X the Core X family.

Top model is the Core i9 7900X, a CPU with 10 cores and a base clock frequency of 3.3 GHz. Thanks to Turbo Boost 3.0 the CPU can reach a maximum of 4.5 GHz in practice. The CPU has an MSRP of $ 999, meaning it is positioned slightly below the 8-core Core i7 6900K from the Broadwell-E generation.

The second model is the Core i7 7820X, a CPU with 8 cores, a base clock frequency of 3.6 GHz and a maximum turbo of 4.5 GHz. This chip has an MSRP of $ 599, roughly comparable with the 6-core Core i7 6850K from the Broadwell-E generation. From this we can conclude that the 7900X and 7820X offer two more cores for the same amount of money compared to a year ago, aside from the other improvements in the Skylake-generation.

The third and last Skylake-X chip is the Core i7 7800X with 6 cores, a base clock frequency of 3.5 GHz and a maximum turbo of 4.0 GHz. This chip has an MSRP of $ 389, which is a lot lower than the 6-core Core i7 6800K from the Broadwell-E generation.

All three Skylake-X processors have a quad-channel DDR4-2667 memory controller and a TDP of 140W. HyperThreading is available for all three chips, meaning that the operating system sees the 10, 8 and 6 cores as 20, 16 and 12 threads respectively. Because of the fact that when you turn off cores a part of the shared L3-cache is turned off as well, this amount differs too: 13.75 MB with the 7900X, 11 MB with the 7820X and 8.25 MB with the 7800X. Something else that is different is the available amount of PCI-Express lanes. Only the top model 7900X offers 44, the other two “only” have 28. This means that you have to choose the top model if you want two graphics cards to use all 16 lanes, or if you want to use three or four graphics cards.

The two Kaby Lake-X CPUs are the Core i7 7740X and Core i5 7640X. They both offer four cores, where the Core i7 has HyperThreading and the i5 does not. In terms of specifications and price they are a lot like the Socket 1151 i7 7700K and i5 7600K. The difference is that the X-models are clocked 100 MHz higher. The CPUs have a TDP of 112W and have a dual-channel DDR4-266 memory controller.

  Clockfr. Turbo 2.0/3.0 Cores / threads L3-cache PCIe 3.0 Memory TDP MSRP
Core i9 7980XE Unknown Unknown 18/36 Unknown Unknown Unknown Unknown $1999
Core i9 7960X Unknown Unknown 16/32 Unknown Unknown Unknown Unknown $1699
Core i9 7940X Unknown Unknown 14/28 Unknown Unknown Unknown Unknown $1399
Core i9 7920X Unknown Unknown 12/24 Unknown Unknown Unknown Unknown $1199
Core i9 7900X 3.3 GHz 4.3/4.5 GHz 10/20 13.75 MB 44 Quad-channel
DR4-2666
140 W $999
Core i7 7820X 3.6 GHz 4.3/4.5 GHz 8/16 11 MB 28 Quad-channel
DDR4-2666
140 W $599
Core i7 7800X 3.5 GHz 4.0 GHz 6/12 8.25 MB 28 Quad-channel
DDR4-2666
140 W $389
Core i7 7740X 4.3 GHz 4.5 GHz 4/8 8 MB 16 Dual-channel
DDR4-2666
112 W $339
Core i5 7640X 4.0 GHz 4.2 GHz 4/4 6 MB 16 Dual-channel
DDR4-2666
112 W $242

As we said before, Intel also announced 12-, 14-, 16- and 18-core models of Skylake-X at Computex. Of these we only know their names and price; Core i9 7980XE ($ 1999), Core i9 7960X ($ 1699), Core i9 7940X ($ 1399) and Core i9 7920X ($ 1199). Other specifications are completely absent. Again, these chips might not be available until 2018.

The announcement of the models with a lot of cores came as a complete surprise during Computex and almost has to have been a last-minute decision in order to have a preemptive answer to AMD’s ThreadRipper processors. After all, it is widely known that AMD wants to release 16-core CPUs for high-end desktops this summer. These are derived from their new Epyc server-CPUs. As it stands now, the ThreadRipper CPUs are released (a lot) sooner than the 12-18 core Intel models and this summer marks the battle between a 16-core AMD Ryzen ThreadRipper and a 10-core Intel Core i9.

When the 18-core models are released as well, the fact remains that the maximum amount of cores available for high-end desktops nearly doubles from generation to generation. If this is not proof that the market for CPUs needed some healthy competition we do not know what is.


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