Tom's Hardware Guide published their preview of the Core 2 Quadro (Kentsfield) processor:
The four cores are not located on a single piece of silicon, but the two Core 2 chips are placed next to each other inside the processor package. Consequently, the transistor count doubles to an impressive 582 million.
We had to do the math as well: More than two Core 2 "Conroe" units do not fit in the existing LGA 775 casing, as the surface is simply not large enough. With a surface area of 143 mm2 per Core 2 dual core, at least 572 mm2 would be required to fit four units (a maximum of 625 mm2 is available). The chips' elongated shape (10.48 mm x 13.63 mm), however, prevents four of them from being accommodated. It is thus safe to say that Intel has reached its limit with dual dies and four cores with 65-nm production..