The power consumed by the memory hierarchy of a microprocessor can contribute to as much as 50% of the total microprocessor system power, and is thus a good candidate for power and energy optimizations. We discuss four methods for tuning a microprocessors' cache subsystem to the needs of any executing application for low-energy embedded systems. We introduce on-chip hardware implementing an efficient cache tuning heuristic that can automatically, transparently, and dynamically tune a configurable level-one cache's total size, associativity and line size to an executing application. We extend the single-level cache tuning heuristic for a two-level cache using a methodology applicable to both a simulation-based exploration environment and a hardware-based system prototyping environment. We show that a victim buffer can be very effective as a configurable parameter in a memory hierarchy. We reduce static energy dissipation of on-chip data cache by compressing the frequent values that widely exist in a data cache memory.