The efficient use of cache hierarchies is crucial to the performance of uni-processor (desktop) and multi-processor (enterprise) platforms. A plethora of research exists on the various structures and protocols that are of interest when considering caches. To enable the performance analysis of various cache hierarchies and associated allocation/coherence protocols, we developed a trace-driven simulation framework called CASPER -- Cache Architecture Simulation & Performance Exploration using Refstreams. The CASPER simulation framework provides a rich set of features to model various cache organization alternatives, coherence protocols & optimizations, allocation/replacement policies, prefetching and partitioning techniques. In this paper, we describe the methodology behind CASPER, its detailed design and currently supported set of functionalities. CASPER has been used extensively for various research studies; a brief overview of some of these CASPER-based evaluation studies and their salient results will also be discussed. Based on its wide-ranging applicability, we believe CASPER is a useful addition to the performance analysis community for evaluating cache structures and hierarchies of various kinds.