Computer graphics processing and selective visual display system – Computer graphics processing – Graph generating
Patent
1995-06-22
1997-09-16
Swann, Tod R.
Computer graphics processing and selective visual display system
Computer graphics processing
Graph generating
345525, 345190, G06T 1530
Patent
active
056689411
ABSTRACT:
A method and apparatus for improving performance of bit block transfers in display controllers during clipping functions without significantly increasing gate count. In a clipping function, particularly when transferring a portion of a monochrome bit map and color expanding same or in pattern copying, a source start address may not lie on a byte boundary. In order to avoid using time consuming shift left operations in software, the source start address may be adjusted in hardware to an earlier byte boundary. Upon writing data to a destination address, a hardware byte mask may be employed to prevent writing of the additional data retrieved due to the adjustment of the source start address. The source start address and byte mask hardware may be implemented in hardware using bit block transfer engine components and a small amount of additional hardware. The remainder of the clipping functions may remain in software, for example in a display device driver. By eliminating the shift left operations from the software portion of the clipping function, overall system performance is enhanced.
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"Graphic BIT-BLT Copy Under Mask", IBM Technical Disclosure Bulletin, vol. 28, No. 6, pp. 2721-2724 Nov. 1985.
Cirrus Logic Inc.
King , Jr. Conley B.
Swann Tod R.
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