1. A system comprising: a memory controller, wherein the memory controller comprises a system cache; and a plurality of agents, wherein the plurality of agents are configured to generate requests which are conveyed to memory via the memory controller; wherein the system cache is configured to: detect an address conflict between a first request and a pending second request, wherein the second request is older than the first request, wherein the first request is generated by a first agent, wherein the second request is generated by a second agent, and wherein the first request has a higher quality of service (QoS) level than the second request; and cause the second request to be expedited responsive to detecting the address conflict between the first request and the second request.