1. A method of data processing in a data processing system, comprising: controlling access to a system memory utilizing a distributed memory controller including a memory channel interface coupled by a memory channel to a memory buffer interposed between the memory channel interface and the system memory; in response to snooping a read-type memory access request of a requestor on a system fabric of the data processing system, the memory channel interface forwarding the read-type memory access request via the memory channel to the memory buffer and starting a timer; in response to the forwarded read-type memory access request, the memory buffer performing a lookup of a target address of the read-type memory access request in a memory controller cache; in response to the lookup resulting in a hit in a coherence state permitting provision of early data, the memory buffer providing a response to the memory channel interface indicating early data and providing a copy of a target memory block of the read-type memory access request to the memory channel interface; and the memory channel interface, responsive to receipt prior to expiration of the timer of the response from the memory buffer indicating early data, transmitting the copy of the target memory block to the requestor via the system fabric prior to receiving a combined response of the data processing system to the read-type memory access request.