A data processing system includes a plurality of processing unit. Each processing unit includes notification storage circuitry configured to store a notification indicator corresponding to each processing unit which indicates whether the processing unit has an outstanding coherent memory request, and multiple request storage circuitry configured to store a multiple request indicator corresponding to each processing unit which indicates whether the processing unit has more than one outstanding request. The data processing system also includes an interconnect network coupled between the processing units and configured to broadcast coherent memory requests from a requesting processing unit of the plurality of processing units to other processing units of the plurality of processing units.