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



A new high-end desktop platform usually means a new challenge for die-hard overclockers that want to set new records. This is no different with Skylake-X and multiple motherboard manufacturers have announced X299 motherboards specifically meant for overclocking.

If you have experience overclocking Broadwell-E or another recent Intel platform, it is good to know that not a lot has changed. All Skylake-X and Kaby Lake-X processors have an unlocked multiplier, which is the most convenient way of overclocking. Of course you can also increase the bClk, but this is purely for the finishing touch. The available voltages that you can change are identical to those of Broadwell-E. Because of this, our Broadwell-E overclock workshop can be used for Skylake-X without any changes.

However, there is something new for overclockers. First of all, the introduction of AVX-512 also comes with an extra multiplier. Because AVX-512 instructions require a lot of power, the processors automatically work at a lower clock frequency when these instructions come by. This so-called offset can be changed in the BIOS of most X299 motherboards. That said, there are no known overclock benchmarks that use AVX-512 (yet). In practice you will not use this offset a lot. There is also a new voltage for the memory controller, the “trim” voltage. At the time of writing we do not exactly know what it does, but increasing it should allow for a slightly higher clock frequency. Last but not least, with Skylake-X it is possible to overclock the PCI-Express controller (and with that the DMI controller). You should not expect any miracles here, but it might be the difference between the first and second place in 3D-benchmarks.

If we listen to motherboard manufacturers we hear that primarily the overclocking of memory is something that Skylake-X does well. Speeds of up to DDR4-4000 are possible with nearly every CPU. With motherboards that have one instead of two DIMM-slots per channel you can easily add 200 MHz to this, and during Computing multiple manufacturers were able to show significantly higher speeds.

During Computex a team of overclockers was able to set nine new world records with Skylake-X. However, the Kaby Lake-X processors were the ones that were able to achieve the highest clock frequencies: thanks to liquid helium a Kaby Lake-X was clocked at 7.577 MHz, a record for a Core i7!

In the near future we will go into more detail about the overclock possibilities of Skylake-X.

The world records achieved with Skylake-X as found on

7.577 MHz with the Core i7 7740X Kaby Lake-X, achieved by overclocker der8auer

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