1. A coherency controller comprising: a primary interface to receive requests and provide responses to an initiator; a secondary interface to send requests and receive responses from a target; a snoop interface to send snoops and receive snoop responses from a coherent agent; and a data store, comprising buffers, and a capacity, that stores data received from the snoop interface, wherein a volume of data requested in transactions pending from the primary interface can exceed the capacity of the data store.