And I do need to add more text to that title line, as that is a 2.9 GHz base-clock compared to the 10-core Core i9 7900X. In late August you should be able to pickup the 12 core Core i9 7920X. 

And that makes things interesting as I immediately want to compare towards Ryzen Threadripper here. AMDs 12-core part will have a 600 MHz faster base clock at 3.5 GHz (boost 4.0 GHz). Now that doesn't mean that the 12-core part from Intel will be slower, they do have more play in the turbo clocks of course. So time will tell what will be the better option. However looking at the recent power consumption numbers on the 10-core part, Intel can't go too wild on the boost frequencies.

 
Intel's 12-core Skylake-X based is to cost 1189 USD. The Ryzen Threadripper 1920X is the 12-core counter-part, that base clock is a notch higher at 3.5 GHz with precision boost to 4.0 GHz, thus SKU will get 24 threads. This processor will retail for 799 USD. This info was spotted by Dutch HWI and is listed in the Intel price-list.

12-core Intel Core i9 7920X will get a 400 MHz slower base-clock