Importance

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Abstract

A VGA compatible graphics controller receives character data, attribute data and font data, each of which are stored in different planes of a display memory. The font data comprises bit maps of at least two character fonts, which may be user fonts or default fonts loaded from a controller BIOS. The video controller detects attempts by a host CPU to write data into plane two of display memory (where character font bit maps reside). The address generated by the host CPU is scrambled to produce a video font cache address. The character font bit maps are stored in a video font cache at the scrambled address. The font select bits of the CPU generated address are used as a byte select to store a particular font at a byte location at a selected video font cache address. In the preferred embodiment, eight fonts may be stored in the video font cache, one scan line each font of each character as a different byte at each address of the video font cache in a 64 bit wide DRAM.

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First Claim