1. A computer program product for implementing selectively powering up a cache set of a multi-set associative cache, the computer program product comprising: a tangible storage medium readable by a processing circuit and storing instructions for execution by the processing circuit for performing a method comprising: receiving an instruction fetch address; based on determining that the instruction fetch address corresponds to one of a plurality of entries of a content addressable memory, identifying, by a computer, a cache set of the multi-set associative cache that contains a cache line referenced by the instruction fetch address, wherein only a subset of cache sets are powered up; based on the identified cache set not being powered up, selectively powering up the identified cache set of the multi-set associative cache; transmitting one or more instructions stored in the cache line referenced by the instruction fetch address to a processor.