I'm able to get 4.2 @ 1.424V game stable arround 39-72°C load in game (gta5 2160P, 980Ti basic amp by Zotac that will black screen on me if I push it past 122% for over a minnute(poor VRM cooling?), OC to 1420/3900 99-118% load in a "turn it up to 130" modded bios.... so easy).... No hitches or stuttering, my asus Z170 S (sabertooth), however it is is garbage.... The rated XMP corsair memory will not run at the timings, or speed deemed okay be both manufactures, I have gone through 2 $200 Gigabyte motherboards as well, a total of three boards, and a different ram kit....... only to be certain the thermal grease they used to save $0.08 between the heat spreader and CPU die is also garbage.
The Asus Z170A is the highest FPS in game with the settings at very low detail @ 640 x 480
The 6700K (K=Overclockers chip.....Yeah right...) maybe not a butter smooth gamers chip, if you look at most current title games they suffer at higher clock with this cpu, , per my findings on the interwebs and in person.
I am going to buy a new one of both....