When designing real-time systems, predictability is of utmost importance. A locking cache is a cache memory that allows loading and locking instructions, thus avoiding their replacement. This way, regarding memory accesses, execution time of instructions is constant since it does not depend on the sequence of memory references. With a predictable behaviour, locking cache memories are a practical alternative to conventional caches for real-time systems. Offering similar performance to conventional caches, locking caches allow an accurate yet simple schedulability analysis.