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Intel CPUs with family 0x6, model 0xE and later (i.e., Intel Core(TM)) have a PMC architecture that differs somewhat from previous CPUs in family 0x6. Even though the basic programming model is similar, the documented set of legal values that may be loaded into their PMC MSRs differs from that of the previous PMCs in family 0x6 and reusing bit values valid for the older PMCs could result in undefined behaviour in the general case.