PC with multiple video-display refresh-rate configurations using active and default registers

A method of automatically configuring an external display monitor connected to a personal computer (PC), the method comprising the computer-implemented steps of:

• polling an external display monitor connected to the PC for a configuration sequence;
• reading the configuration sequence from the external display monitor;
• when the external display monitor does not return the configuration sequence:
• reading a default refresh rate from a default register;
• writing the default refresh rate to an active refresh-rate register on a graphics controller, and writing timing values to timing registers on the graphics controller, the timing values generating a vertical synchronization signal to the external display monitor at a frequency indicated by the active refresh-rate register;
• when the external display monitor returns the configuration sequence:
• calculating a maximum refresh rate from the configuration sequence;
• writing the maximum refresh rate to the active refresh-rate register on the graphics controller, and writing timing values to the timing registers on the graphics controller, the timing values generating the vertical synchronization signal to the external display monitor at a frequency indicated by the active refresh-rate register, and
• retaining the default refresh rate when the active refresh-rate register is written, wherein the default refresh rate is not over-written during auto-configuration when the active refresh-rate register is written,
• whereby the graphics controller is automatically configured for the external display monitor using either the configuration sequence or the default refresh rate.

A computer-program product comprising:

• a computer-usable medium having computer-readable program code means embodied therein for auto-configuring an external CRT, the computer-readable program code means in the computer-program product comprising:
• reading means for reading a system registry file for default refresh rates for a plurality of resolutions;
• writing means for writing the default refresh rates to a default register on a graphics controller chip;
• active-register writing means for writing an active register with a default refresh rate for a current resolution in the plurality of resolutions and for writing CRT timing registers with timing values that generate the default refresh rate;
• calling means for calling a video BIOS extension routine to retrieve configuration information from the external CRT, and determining a maximum refresh rate from the configuration information;
• and
• second writing means for writing the maximum refresh rate to the active register and for writing the CRT timing registers with timing values that generate the maximum refresh rate when the configuration information is returned, but retaining the default refresh rate in the active register when no configuration information is returned,
• whereby the external CRT is auto-configured by the configuration information when returned, or the default refresh rate when configuration information is not returned.