OVERVIEW There is a wide variety of monitors in use today with many iterations of ET4000-based video adapters being used with them. Because of this, a software utility is necessary to make the two components work together by setting horizontal and vertical synchronization frequencies, as well as video system clock rates. The screen that you see on your monitor actually has to be re-projected repeatedly in order for you to see it clearly. The rate at which each line is displayed horizontally (left to right) is the horizontal scan rate. This is measured in kilohertz, a unit of measurement that means one thousand cycles per second. Since it takes longer to project each line across a display than top to bottom, this frequency must be much higher than vertical frequency, which is one cycle per second. Therefore, vertical frequency, or refresh rate (the period of time to re-project the entire screen image from top to bottom) is a more critical measurement as the entire screen being projected is susceptible to exhibiting flicker. The VMODE utility allows users to adjust the rate at which the screen is displayed both in horizontal and vertical terms. Additionally, the video system clock rate, or the oscillator (clock) which sets the basic timing rate capabilities for the video synchronization subsystem, is also adjustable to attain compatibility with various monitor and video adapter designs. Because the variance in these components is so diverse, preset menus to choose synchronization rates are extremely difficult to construct and be reliable. VMODE, then, is a manual approach to garner the best compatibility between monitors and video adapter designs across a very wide range of components. VMODE SCAN RATES The VMODE utility is provided to aid in eliminating flicker and other video distortion exhibited when monitors cannot automatically synchronize to frequencies outputted by video cards. By issuing one or more VMODE commands, many monitors can accommodate different frequencies and greatly improve the display. VMODE commands can be issued from the DOS prompt, batched in the AUTOEXEC.BAT file, or incorporated into separate batch files for starting applications that require settings prior to loading. example (WINN.BAT) VMODE 35K WIN Additional modes are available to provide additional scan rates that may improve synchronization with a variety of monitors. Normally, the default scan rates are effective, but some monitors may require different scan rates for the most satisfactory display results. By setting these modes, frequencies are adjusted that affect displayed graphic modes. The following modes are available via the VMODE command. example: VMODE x VMODE Modes Vertical Horizontal x Value Affected Refresh Rate Frequency Resolution 35K 29,2A,30 56Hz 35KHz 800x600 38K 29,2A,30 60Hz 38KHz 800x600 48K 29,30 72.7Hz 48.4KHz 800x600 45M 37i,38i 86.5Hz 35.5KHz 1024x768 * 65M 37n,38n 60.5Hz 49KHz 1024x768 ** * interlaced ** non-interlaced 72HZ Modes The following graphic (not text) modes can be displayed after setting the vertical refresh rate to 72HZ. The 72HZ mode will provide a clearer display with less flicker on some monitors. Set the VMODE parameter to VMODE 72HZ. After this is done you can use VMODE to set the display to any of the graphic modes listed below. VMODE Modes Vertical Horizontal x Value Affected Refresh Rate Frequency Resolution 72HZ 11 72.70Hz 38.70KHz 640x480* 72HZ 12 72.70Hz 38.70KHz 640x480* 72HZ 25 72.70Hz 38.70KHz 640x480* 72HZ **2E 72.70Hz 38.70KHz 640x480* * monitor must be capable of 72.70Hz vertical and 38.70KHz horizontal frequency. ** requires minimum of 512kb display memory; 45/65 MHZ Modes (45m, 65m) The following graphic (not text) modes can be displayed after setting the system video clock rate to 45 or 65MHz. These modes will provide a clearer display with less flicker on some monitors. Set the VMODE parameter to VMODE 45m or 65m. After this is done you can use VMODE to set the display to any of the graphic modes listed below. VMODE Modes Vertical Horizontal x Value Affected Refresh Rate Frequency Resolution 45m 37i,38i 86.96 35.52 1024x768 65m 37n,38n 60.58 48.95 1024x768 72/75/80 MHZ Modes (72m, 75m, 80m) The following graphic (not text) modes can be displayed after setting the system video clock rate to 72MHz. The 72MHz mode will provide a clearer display with less flicker on some monitors. Set the VMODE parameter to VMODE 72m. After this is done you can use VMODE to set the display to any of the graphic modes listed below. VMODE Modes Vertical Horizontal x Value Affected Refresh Rate Frequency Resolution 72m 37 69.80 56.30 1024x768 72m 38 69.80 56.30 1024x768 75m 38n 69.10 56.48 1024x768 80m 38n 72.00 57.80 1024x768 80m 3Di 87.02 48.00 1280x1024 NOTE: Choose modes/resolutions that are compatible with your video board configuration and monitor capabilities. Typing VMODE ? will display the full array of mode possibilities. Users that are familiar with the characteristics of their monitors will find these modes more useful. See Appendix D for definitions of available modes. Note that choosing VMODE 60HZ will return the adapter to normal operation.