Browse Prior Art Database

Hardware Display Windowing System

IP.com Disclosure Number: IPCOM000060724D
Original Publication Date: 1986-May-01
Included in the Prior Art Database: 2005-Mar-09
Document File: 2 page(s) / 39K

Publishing Venue

IBM

Related People

Lisle, RJ: AUTHOR

Abstract

The figure illustrates a hardware implementation of existing software windowing packages. These software packages for performing display windowing and display sharing by multiple processors result in a relative high overhead for the system. The above arrangement performs the mapping of multiple display buffers to the physical display screen via address translation of the Cathode Ray Tube Controller (CRTC) address lines. Instead of software mapping and transferring the contents of multiple window buffers to a single display buffer, the CRTC fetches display data directly from the window buffers for each window, transparently to applications or operating system. This is accomplished as follows in the system shown in the figure.

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Hardware Display Windowing System

The figure illustrates a hardware implementation of existing software windowing packages. These software packages for performing display windowing and display sharing by multiple processors result in a relative high overhead for the system. The above arrangement performs the mapping of multiple display buffers to the physical display screen via address translation of the Cathode Ray Tube Controller (CRTC) address lines. Instead of software mapping and transferring the contents of multiple window buffers to a single display buffer, the CRTC fetches display data directly from the window buffers for each window, transparently to applications or operating system. This is accomplished as follows in the system shown in the figure. "Window Position Buffers" 11 contain starting and ending row and column numbers for every window and their priority or "z" coordinate. "Address Compare" block 12 performs four comparisons for each window: 1) start row <scan row; 2)end row > >scan column. If all four comparisons are true, then an "in-window" signal 13 is sent to the priority encoder 14. The four compares for each window can be performed in parallel, or multiplexed, or a combination of both. "Priority Encode" block 14 accepts an "in- window" signal for each window, and outputs the number of the highest priority active signal based on the "Z" coordinate numbers in the window position buffers. "Scroll Buffers" 15 store a row and column offset for...