After much testing I have determined my i7-6700k, which I purchased late September, is not dissipating heat to the integrated thermal spreader. At idle my temperatures fluctuate quite rapidly between 30 degrees and 60 degrees Celsius. Under a modest real-world usage load with all cores in-use, the temperatures rise to 80-90. I've decided not to run a torture test as I'm already a solid 30 degrees above what I would consider the comfort zone. All of these temperatures aside, my H100i never gets warm. I've re-seated the block around 10+ times and tested a few air coolers with little to no difference at all. I work at a repair shop so I have access to a lot of parts, making it easy for me to test this type of issue. Running the block on an FX-8350 overclocked to 4.4GHz (just below the voltage wall) runs at a maximum of 47 degrees Celsius for the entire duration of a 1-hour Prime95 torture test. I'm aware that I shouldn't expect similar temperatures from different processors, I'm just using the 5-year-old 125-watt overclocked AMD processor as a reference point. At 47 degrees Celsius with the FX-8350 you can feel the heat coming off the radiator. At 90 degrees with the i7 6700k it just feels like cold air, even with the air coolers.
My motherboard is a Gigabyte GA-Z170XP-SLI, running 16 gigs of g.skill RAM at 3200MHz using the default XMP profile. All other BIOS settings are default/auto. I can post temp snapshots or any additional info when I get home from work tonight. I am currently running revision F6 of the BIOS for my board, but there is a new one that just came out last month (F20). The only reason I haven't flashed to it yet is because of the description:
- Support next generation CPU
* This BIOS prohibits updating to earlier version BIOS
I'm a little uncertain of upgrading to any BIOS that prevents me from downgrading and I've had issues in the past upgrading a BIOS to include 3rd gen processor support.. Thereby disabling support for the 2nd gen processor already in it. If anyone can assure me this is not the case, I'd have no problem trying this upgrade to resolve my issue. I've heard the default voltages on certain motherboards are a bit high and who knows, maybe they fixed it.
I can post temperature snapshots or any other additional information when I get home later tonight. If this can be resolved without resorting to warranty or replacement, I'd be grateful. But I'm not against it.
EDIT: I forgot to mention I recently upgraded to this i7-6700K from an i5-6600K using the same board. Prior to the upgrade my temperatures were as I expected them to be. No issues with that processor whatsoever.