[wtallis]

Core count, clock speed, and cache quantity are related to yield. HyperThreading, VT-d, AVX, Turbo Boost, AES-NI, TSX, and ECC are all too integral to the core design; they're physically present on all chips and it is extremely unlikely for a manufacturing defect to affect one of those features without otherwise crippling the chip. Those features are used for product segmentation that is not driven by any real marginal cost.