Power conservation may be achieved in a front end system by disabling a
segment builder unless program flow indicates a sufficient likelihood of
segment reuse. Power normally spent in collecting decoded instructions,
detecting segment beginning and end conditions and storing instruction
segments is conserved by disabling those circuits that perform these
functions. An access filter may maintain a running count of the number of
times instructions are read from an instruction cache and may enable the
segment construction and storage circuits if the running count meets or
exceeds a predetermined threshold.