FWIW I have 2 retail E5-2683 V3 chips(s-spec SR1XH) for sale on eBay. These are 14c/28t They are not engineering samples. They are OEM final production chips. They aren't cheap but when you consider they retail for $2100+ the price is good IMHO. In a 2P SuperMicro board running 56 threads @ WCG they pulled 270 watts total at the wall. The stock clock is 2.0 Ghz. They turbo up to 2.3GHz under full load. Anything turbo mode you see listed above 2.3 is for a single thread, not all 56.
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EDIT: These chips will run in some X99 boards but may require a BIOS update. I've read that they work in Asus and AsRock mobos. Don't know about others.