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Current on-chip block-centric memory hierarchies exploit access patterns at the fine-grain scale of small blocks. Several recently proposed memory hierarchy enhancements for coherence traffic reduction and prefetching suggest that additional useful patterns emerge with a macroscopic, coarse-grain view. This paper presents RegionTracker, a dual-grain, on-chip cache design that exposes coarse-grain behavior while maintaining block-level communication. RegionTracker eliminates the extraneous, often imprecise coarse-grain tracking structures of previous proposals. It can be used as the building block for coarse-grain optimizations, reducing their overall cost and easing their adoption. Using full-system simulation of a quad-core chip multiprocessor and commercial workloads, we demonstrate that RegionTracker overcomes the inefficiencies of previous coarse-grain cache designs. We also demonstrate how RegionTracker boosts the benefits and reduces the cost of a previously proposed snoop reduction technique.