United States Patent 5,936,616 describes a method and system for accessing and displaying a compressed display image in a computer system. The invention provides a display controller that maintains the primary display image in compressed subregions or chunks. The controller emulates a conventional frame buffer by making the compressed image appear as if it has a linear address space. Most of the image is compressed, and the remainder is selectively decompressed and cached to satisfy read and write requests. The controller decompresses the display image's constituent subregions and buffers the decompressed data so that it can be scanned out to a display monitor. The display controller includes a cache for storing decompressed subregions of the display image, a compressed memory for storing compressed subregions, and a virtual frame buffer controller for controlling read and write accesses to the cache. The controller can use lossy or lossless compression for the subregions. The virtual frame buffer controller makes the display image appear as if it resides in a linear address space, allowing compatibility with existing display software. For write requests, the controller can allow a write to the cache without decompressing a corresponding compressed subregion until later, merging new pixels with the compressed image in the background. The invention reduces memory requirements by storing the display image in compressed form, which occupies less memory than a frame buffer used to store an entire frame of a decompressed image. It also reduces memory bandwidth requirements since compressed data requires less bandwidth to transfer than decompressed data. The virtual frame buffer control maintains compatibility with existing display software by supporting linear addressing used to read or write pixels to a conventional frame buffer. The display controller can be implemented in software or hardware, and the invention provides several advantages, including reduced memory usage, lower bandwidth requirements, and compatibility with existing display software. The invention is implemented in a variety of ways, including using a combination of host computer resources and display controller resources. The display controller includes a virtual frame buffer controller, cache memory, decompressor, compressor, compressed memory, and compositor. The compositor retrieves compressed subregions, decompresses them, and combines them into a display image. The invention allows for efficient pixel write operations and ensures that the compressed display image accurately reflects the display image on the monitor.United States Patent 5,936,616 describes a method and system for accessing and displaying a compressed display image in a computer system. The invention provides a display controller that maintains the primary display image in compressed subregions or chunks. The controller emulates a conventional frame buffer by making the compressed image appear as if it has a linear address space. Most of the image is compressed, and the remainder is selectively decompressed and cached to satisfy read and write requests. The controller decompresses the display image's constituent subregions and buffers the decompressed data so that it can be scanned out to a display monitor. The display controller includes a cache for storing decompressed subregions of the display image, a compressed memory for storing compressed subregions, and a virtual frame buffer controller for controlling read and write accesses to the cache. The controller can use lossy or lossless compression for the subregions. The virtual frame buffer controller makes the display image appear as if it resides in a linear address space, allowing compatibility with existing display software. For write requests, the controller can allow a write to the cache without decompressing a corresponding compressed subregion until later, merging new pixels with the compressed image in the background. The invention reduces memory requirements by storing the display image in compressed form, which occupies less memory than a frame buffer used to store an entire frame of a decompressed image. It also reduces memory bandwidth requirements since compressed data requires less bandwidth to transfer than decompressed data. The virtual frame buffer control maintains compatibility with existing display software by supporting linear addressing used to read or write pixels to a conventional frame buffer. The display controller can be implemented in software or hardware, and the invention provides several advantages, including reduced memory usage, lower bandwidth requirements, and compatibility with existing display software. The invention is implemented in a variety of ways, including using a combination of host computer resources and display controller resources. The display controller includes a virtual frame buffer controller, cache memory, decompressor, compressor, compressed memory, and compositor. The compositor retrieves compressed subregions, decompresses them, and combines them into a display image. The invention allows for efficient pixel write operations and ensures that the compressed display image accurately reflects the display image on the monitor.