Real time virtual window management for bit mapped raster graphics

In this paper we present a hardware real time window system which uses a virtual address mapping scheme based on associative memory. Until now, bit block transfer operations were used to update screen contents from main memory window information. Since these operations transfer large blocks of data from main memory to the frame buffer whenever window parameters are changed, response times of window systems were slow. With the proposed approach, the frame buffer may be completely eliminated and replaced by a large virtual video memory which is capable of holding all the window data in non-overlapping locations. Mapping becomes now a dynamic real-time function which assigns screen addresses to different areas of the virtual video memory at different times.