Importance

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Abstract

A portable personal computer (PC) can be connected to a variety of different external CRT monitors. Configuration of each CRT monitor is performed by the graphics display driver software so that the user does not have to re-configure the graphics sub-system every time a different CRT monitor is connected. Auto-configuration of Plug-and-Play monitors occurs by reading configuration information from the monitor itself. For Windows 95, the Plug-and-Play drivers are used for auto-configuration, or for older operating systems the video BIOS display-data-channel functions is used. Older 'legacy' CRT monitors that do not support Plug-and-Play are still auto-configured. The vertical refresh rate for each resolution is stored in a default register on the graphics controller chip. The vertical refresh rate from default register is copied to an active refresh-rate register when a legacy (non Plug-and-Play) monitor is detected. When a Plug-and-Play monitor is detected, the refresh rate is calculated and written to the active refresh-rate register, without overwriting the default registers. Thus a Plug-and-Play monitor can be connected without losing configuration information for the legacy monitors. A Plug-and-Play flag is also added to the graphics controller chip to disable the video BIOS auto-configuration when Windows 95 is used.

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First Claim