Method for preserving memory request ordering across multiple memory controllers

A method for preserving ordering of memory requests distributed across multiple memory controllers, comprising:

• receiving a memory request at a first memory controller, the memory request including a source tag indicating a source from which the memory request originated;
• comparing the source tag with source tags for pending memory requests in a second memory controller to determine if the second memory controller contains any pending memory requests from the same source;
• wherein the source tags for the second memory controller are stored within the first memory controller;
• if the second memory controller contains pending memory requests from the same source, stalling the first memory controller until the pending memory requests within the second memory controller from the same source complete;
• issuing the memory request from the first memory controller to a first random access memory coupled to the first memory controller;
• propagating the source tag for the memory request to the second memory controller so that the second memory controller can compare source tags for subsequent requests received at the second memory controller against source tags for pending memory requests in the first memory controller;
• receiving a response from the first random access memory indicating that the memory request has been completed;
• and
• if the memory request is a read operation, returning read data to the source from which the memory request originated.