Computer graphics processing and selective visual display system – Display peripheral interface input device – Light pen for fluid matrix display panel
Patent
1994-01-03
1995-12-19
Hjerpe, Richard
Computer graphics processing and selective visual display system
Display peripheral interface input device
Light pen for fluid matrix display panel
345203, G09G 500
Patent
active
054772427
ABSTRACT:
Method and apparatus for enabling an XGA display adapter selectively to support VGA graphics mode virtualization during native mode operation of the adapter by rendering VGA graphics assist hardware and certain VGA registers accessible. In a preferred embodiment, the invention comprises an XGA display adapter which includes a host interface for interfacing the display adapter with a central processing unit (CPU) of a personal computer (PC), VGA graphics assist hardware for performing VGA graphics assist functions, a memory controller for reading and writing a video memory of the PC as requested by the CPU during video memory accesses, and a display interface for generating control and timing signals to a display of the PC. The XGA display adapter also includes a XGA Operating Mode Register having three control bits which can be written by applications software selectively to enable or disable the virtual VGA function of the present invention. When the virtual VGA function is enabled, logic circuitry within the host interface examines the CPU address associated with each video memory access to determine whether the access comprises a virtual VGA memory access, rather than a native memory access. If so, the host interface routes CPU address and any data to be written to the video memory at that address, which performs the appropriate graphics assist operations on the address and/or data to enable the requested operation accurately to be performed on a virtual VGA memory buffer portion of the video memory by the memory controller.
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Brannon Sherwood
Rackley Darwin P.
Thompson Stephen P.
Hjerpe Richard
International Business Machines - Corporation
Liang Regina
McKinley Martin J.
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