AC/DC is an adaptive method for prefetching data from main memory. The basic prefetch method divides the memory address space into equal-sized concentration zones (CZones), and uses a global history buffer to track and detect patterns in miss address "deltas" (differences between consecutive addresses) within each CZone. When simulated with a realistic desktop memory system, CZone prefetching with Delta Correlations (C/DC) outperforms four other previously proposed prefetching methods. C/DC yields an average performance improvement of 23 percent when compared with no prefetching. Adaptively is then added to the basic method. A tuning algorithm dynamically configures the CZone size and prefetch degree (i.e. the amount of data prefetched) on a per program-phase basis. Adaptive re-configuration provides additional performance improvements of 4% over C/DC. Overall, the Adaptive CZone / Delta Correlation (AC/DC) method outperforms other methods studied by 10%.