Memory controller with virtual controller mode

A memory controller having a memory channel controller with a virtual controller mode, the memory channel controller comprising:

• an address generator for receiving memory access requests and decoding said memory access requests to select a rank and bank of memory devices in a memory system, and in the virtual controller mode further decoding a sub-channel number of a plurality of sub-channels for each of said memory access requests;
• a command queue coupled to said address generator for storing said decoded memory access requests, including said sub-channel number in the virtual controller mode;
• an arbiter coupled to said command queue to select memory access requests from said command queue using said rank and said bank according to predetermined criteria, and in the virtual controller mode selecting from among said memory access requests in each sub-channel independently using said predetermined criteria;
• and
• a dispatch queue coupled to said command queue for dispatching selected memory commands to a memory system over a physical interface, and in the virtual controller mode further dispatching said selected memory commands to a selected sub-channel.

A data processing system comprising:

• a plurality of memory channels;
• a memory controller coupled to said plurality of memory channels and having a memory channel controller with a virtual controller mode, said memory channel controller comprising:
• a command queue for storing memory access requests including a sub-channel number in said virtual controller mode;
• and
• an arbiter coupled to said command queue to select memory access commands from said command queue according to predetermined criteria, wherein in said virtual controller mode said arbiter selects from among said memory access requests in each sub-channel independently using said predetermined criteria, and sends selected memory access requests to a one of said plurality of memory channels corresponding to said sub-channel number.

A method for controlling a memory system having a plurality of memory channels, comprising:

• in a virtual controller mode:
• receiving memory access requests;
• decoding each of said memory access requests into a bank, a rank, and a sub-channel of a plurality of sub-channels of memory devices in the memory system;
• storing said memory access request including said bank, said rank, and said sub-channel in a command queue;
• selecting from among a plurality of memory access requests in said command queue using predetermined criteria, wherein said selecting further comprises selecting from among said memory access requests to each sub-channel independently using said predetermined criteria;
• and
• dispatching said memory access requests, so selected, to one of the plurality of memory channels according to said sub-channel.