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Yes.
Each series features a different microarchitecture and transistor size. The 1st generation is a 45 nanometer transistorized circuit that is designed for the Nehalem architecture. It also features dual, quad, and hexa core CPU's.
the 2nd generation is a 32 nanometer transistorized circuit that is designed for the Sandy Bridge architecture. It also features hexacore CPU's with an integrated Graphics processor or IGP.