System and method for using a page tracking buffer to reduce main memory latency in a computer system

Abstract

A memory controller for a memory subsystem of a computer system connects to a processor bus. The memory controller is for use with memory devices such as RDRAM or DDR SDRAM that allow for multiple open pages. Memory references are remapped by an address mapper and processed by a page tracking buffer to keep track of open pages in the memory devices. The controller also has a state machine, and an interface to memory devices. The page tracking buffer has a row address content addressable memory for determining when a reference is in an open page, and a bank content addressable memory for determining when a reference is to the same bank as an open page. The controller closes open pages of a bank prior to opening new pages in that bank. The page tracking buffer has fewer lines than the product of the maximum number of memory devices times the maximum number of simultaneously open pages of each device, but provides for tracking any page of any of the memory devices.