MECHANISM ALLOWING ASYNCHRONOUS ACCESS TO GRAPHICS ADAPTER FRAME BUFFER PHYSICAL MEMORY LINEAR APERTURE IN A MULTI-TASKING ENVIRONMENT

摘要

A module is interposed between a multitasking operating system and the devicedriver fora graphics adapter including a frame buffer with a linear aperture forcontinuous, asynchronous datatransfers. The interposed module may selectively intercept all graphics devicedriver functionrequests or simply pass such requests to the device driver, and provides amechanism for generatinggraphics output in the frame buffer without utilizing graphics acceleratorhardware on the graphicsadapter. The interposed module is aware of the start and stop of asynchronousdata transfers to theframe buffer. When asynchronous data transfers are started, the interposedmodule invokes thegraphics adapter device driver to obtain access to the frame buffer linearaperture and sets its owninternal state to active. While active, the interposed module intercepts allgraphics device driverrequests and employs its own mechanism to generate graphics output in theframe buffer responsiveto such requests, without utilizing the graphics accelerator hardware. Sincethe graphics acceleratorhardware is not utilized, the frame buffer linear aperture always remainsenabled. While inactive,the interposed module simply passes all graphics device driver requests to thedevice driver. Theinterposed module is preferably implemented in accordance with the GRADDarchitecture model,with the mechanism for generating graphics output being provided by the VMANand SOFTDRAWlibraries.