Memory controller and method of memory access sequence recordering that

Abstract

An improved memory controller is disclosed for accessing a computer memory, which consists of a plurality of banks of page mode memory cells and is connected to a CPU via a split transaction bus with out-of-order completion capability. The improved memory controller comprises: (a) a unified command queue for receiving a memory access command; (b) a plurality of command queues equalling in number to the number of the memory banks; (c) a dispatch logic for dispatching the memory access command into one of the command queues in accordance with which memory bank the access command is to access; (d) a selection logic for selecting one of the command queues as an active command queue to execute a command, wherein all the non-selected command queues are placed on a standby status as standby command queues; and (e) switching logic provided in the selection logic for switching the command execution from the active command queue to a standby command queue, which is made active according to a predetermined criterion, when a page miss is detected or when the active command queue is empty. The switching logic also causes one of the standby command queues to perform a row address selection when the active command queue is accessing said computer memory. With the improved memory controller, penalties associated with row miss and/or page miss are eliminated. As a result, the average memory access latency is minimized and overall memory utilization efficiency is enhanced.