Could hyperthreading be hurting with 6 cores? or is it the cache speed? Or the low base clock? Almost all the reviews show instances of the 8700k falling behind the 7700k in several games (usually not by much but still). Tbh it's all over the place right now, I cancelled my pre-order and will wait it out. And I hate Intel for not giving detailed specs anymore. It's a complete lottery what voltage/frequency/temps you'll get at stock nowadays. Heck ASUS is even unstable at stock settings because of MCE...
Also I see Kyle wasn't able to get his RAM to run at 4000mhz with the motherboard I was purchasing. Not good.
If an application forces all the cores active but doesn't use them well, I think the 8700k would drop in frequency to areas where it had no real advantage over the 7700k. If the cores aren't fully loaded, the developers are better off using fewer threads. It's a balancing act which is unbelievably annoying.
That should be pretty rare, as overwhelmingly most usages are either strictly single threaded or threaded pretty well (encoders, compressors, etc).
Games will be and always have been really difficult to get perfectly right on all CPUs, due to the pseudo-realtime nature of them. Getting all subtasks to finish at the same time for the frame is tough given core sharing (hyperthreading), timing changing as a function of core loading (turbo), and then of course differing architectures (AMD vs Intel). You miss things even a tiny bit and it is perceivable stutter, especially on fixed rate displays. Its wildly complicated and is why you only see a handful of titles that consistently run buttery smooth.
tbh, i think its more to do because there are more cores, longer ring bus, waiting for more cores to respond for info means higher latency, so in general it should make sense if its a tiny bit slower. didn't they run bench test and its just below 1% which is well within margin of error, no need to care about that sort of stuff.