We have already noted that, formally, Core i7-3820 refers to the stepping M1, and this processor can exist even prior to stepping M0.
Even the six-core Core i7 processors LGA 2011 will actually have an eight-chip, just extra two cores are disabled. Fully eight cores active in store for the server segment, where the processors will be offered as Sandy Bridge-EP. Origin Quad Core i7-3820 can be explained by the existence of crystals Sandy Bridge-E, in which half of the cores are disabled.
Associate however believe that Core i7-3820 is based on special quad-chip, on which there is no extra cores. The area of this crystal is about one-third less than six-and eight-analog. Accordingly, in the production such processors are cheaper. Among the processors Xeon E5-generation Sandy Bridge-EP there is also a model with four core stepping M0. The new chip is mainly used for their production.