Memory bandwidth utilization through multiple priority request policy for isochronous data streams

Abstract

An embodiment of a system logic device for improving memory bandwidth utilization in a computer system with an isochronous data stream includes a FIFO for the isochronous data stream. The FIFO includes two watermarks. When the data level of the FIFO falls below a first watermark level, a low priority request is issued to a memory controller. If the data level of the FIFO falls below a second watermark level, a high priority memory request is issued to the memory controller. The low priority memory request is assigned the lowest priority level by the memory controller. The high priority request is assigned the highest priority level by the memory controller. The low priority request allows the isochronous data stream to retrieve small amounts of data from memory without negatively impacting overall system performance while the high priority request allows the isochronous data stream to retrieve larger amounts of data from memory within a fixed time in order to ensure that the FIFO never completely drains.