Signalling for heterogeneous memory systems

A method, comprising:

• receiving a plurality of memory access requests including volatile memory reads, volatile memory writes, non-volatile memory reads, and non-volatile memory writes;
• placing memory access commands for fulfilling the memory access requests in a memory interface queue and transmitting the memory access commands from the memory interface queue to a heterogeneous memory channel coupled to a non-volatile storage class memory (SCM) module including non-volatile memory addressable in a system memory space;
• storing the non-volatile read commands that are placed in the memory interface queue in a non-volatile command queue (NV queue);
• and
• receiving a ready response from the non-volatile SCM module indicating that responsive data is available for an associated one of the non-volatile read commands, and in response to receiving the ready response, placing a send command for commanding the non-volatile SCM module to send the responsive data in the memory interface queue.

A data processing system, comprising:

• a central processing unit;
• a data fabric coupled to the central processing unit;
• and
• a memory controller coupled to the data fabric for fulfilling memory requests from the central processing unit, the memory controller comprising:
• a command queue having a first input for receiving memory access commands including volatile read commands, volatile write commands, non-volatile read commands, and non-volatile write commands, and an output, and having a plurality of entries;
• a memory interface queue having an input coupled to the output of the command queue, and an output coupled to a heterogeneous memory channel which is coupled to at least one non-volatile storage class memory (SCM) module including non-volatile memory addressable in a system memory space;
• a non-volatile command queue (NV queue) coupled to the output of the command queue for storing non-volatile read commands that are placed in the memory interface queue;
• an arbiter coupled to the command queue for selecting entries from the command queue, placing them in the memory interface queue causing them to be transmitted over the heterogeneous memory channel;
• and
• control logic coupled to the heterogeneous memory channel for receiving a ready response from the non-volatile SCM module indicating that responsive data is available for an associated one of the non-volatile read commands, and in response to receiving the ready response, causing a send command to be placed in the memory interface queue for commanding the non-volatile SCM module to send the responsive data.