The chip will be supported by existing LGA2011v3 motherboards but one interesting thing is that the package is somewhat different. It has a thinner fiberglass substrate, it measures 1.12mm vs 1.87mm for the Haswell-E, but has a thicker IHS. You can check out the benchmark screenshots at TechPowerUp.
The i7-6850K sample was installed on a machine with ASRock X99 Extreme3 motherboard (BIOS: P3.30), 16 GB of quad-channel DDR4-2133 memory, and a single GeForce GTX 980 Ti graphics card. It was compared to a Core i7-5820K processor on the same setup. The i7-6850K based setup was barely (~1%) faster at 3DMark FireStrike Extreme in its final score, however, its CPU-intensive Physics score was 14.9% higher. Moving on to the community favorite Cinebench R15, the i7-6850K yielded a 10% higher score. To test its single-core performance, the chip was put through SuperPi 32M, where the i7-6850K crunched through the test in 8m 27.854s, compared to 8m 38.866s by the i7-5820K.