An integrated circuit includes a first communication interface for communicatively coupling the integrated circuit with a coherent data processing system, a second communication interface for communicatively coupling the integrated circuit with an accelerator unit including an effective address-based accelerator cache for buffering copies of data from a system memory, and a real address-based directory inclusive of contents of the accelerator cache. The real address-based directory assigns entries based on real addresses utilized to identify storage locations in the system memory. The integrated circuit further includes directory control logic that configures at least a number of congruence classes utilized in the real address-based directory based on configuration parameters specified on behalf of or by the accelerator unit.