Few pages of overclocking reviewer’s guide on Intel's X299 Kaby Lake-X platform and CPUs has leaked. According to this document a “good” Intel Core i7-7740X chip is supposed to run Cinebench R15 at 5.0 GHz and 1.205v in combination with a potent CPU cooler. If you’re lucky it could even be possible that you’d be able to run your chip at 5.2 GHz, but with higher voltages - of course.
According to the guide, Intel’s Core i7-7740X has a "higher overclock ceiling" than the Core i7-7700K, in other words the new quad core might be faster in single-thread applications. However the real improvement over Intel Z270 might be tiny. In the end it will be very hard to justify why to buy X299 based platform over the already existing Z270 offerings, since the price difference is going to be well noticeable, just to say the least.
Nevertheless, according to the graph that has leaked, a “good” chip should be capable of running Cinebench R15 at 5.1 GHz with 1.255v, while with a “bad” chip you’ll have to raise the voltage to 1.41v.
Due to the limited memory options (dual-channel on Z270 instead of quad-channel on Intel X299), core counts (only quad core) and PCIe lanes (16 lanes), we believe that moving from the Z270 to the X299 platform would be a rather questionable choice. The only major difference between Z270 and X299 is in fact the quad-channel memory interface. Apart from that there are other details that would really justify “upgrading” from Z270 to X299. Furthermore, Instel is not soldering the heat spreader to the die, which means that if you’re planning on overclocking your chip using air cooling or even custom water cooling, temperatures are going to be high. In fact the temperatures are going to be similar to Skylake and/or Kaby Lake.
Source:
Videocardz