It has been released on June 2017 and the 12-core i9-7920X will be release on august 2017.
These are the differences between i9 and i7.
The difference between x299 chipset and x99 chipset.
The 10-core Core i9-7900X is quicker in every test than a Ryzen 7 1800X.
Here are the stats.
Read next
From @gabykes