Method and apparatus for providing and maximizing concurrent operations in a shared memory system which includes display memory

Abstract

The present invention provides a low-cost computer system which includes a single sharable block of memory that can be independently accessible as graphics memory or main store system memory without performance degradation. Because the “appetite” for main system memory (unlike that of a display memory) is difficult to satisfy, the memory can be addressed by reallocating an unused portion of a display memory for system memory use. Reallocation of the unused display memory alleviates any need to oversize the display memory, yet realizes the cost effectiveness of using readily available memory sizes. Further, reallocation of the graphics memory avoids any need to separately consider both the system memory and the display memory in accommodating worst case operational requirements. In accordance with additional embodiments, improved efficiency of operation can be achieved to enhance concurrency between plural banks of memory when expansion memory is included. The addressable locations of the expansion memory can be mapped to the bottom of the available system address space, and addressable locations of any prior base system memory are moved above the expansion memory space.