Tuning a configurable cache subsystem to an application can greatly reduce memory hierarchy energy consumption. Previous tuning methods use a level one configurable cache only, or a second level with separate instruction and data configurable caches. We instead use a commercially-common unified second level, a seemingly minor difference that actually expands the configuration space from 500 to about 20,000. We develop additive way tuning for tuning a cache subsystem with this large space, yielding 62% energy savings and 35% performance improvements over a non-configurable cache, greatly outperforming an extension of a previous method