Monitor Drivers

A monitor driver contains the range of parameters that a monitor can support. The display mode is a specific subset of those parameters. The display mode you choose must be compatible with your monitor or your screen display may be distorted.

A display mode is defined by:

• Resolution (horizontal and vertical dimensions in pixels)
• Vertical and horizontal scan rates (the speed at which the monitor updates the display)
• Color palette (the largest number of colors that can be displayed on the screen at one time and the size of the palette from which the displayable colors can be chosen)

To determine if you can use a particular display mode, check the horizontal and vertical scan rates listed in this section against the specifications for your monitor. If the display mode's scan rates are outside your monitor's acceptable range, you cannot use the mode.

When choosing a monitor and monitor driver, you should consider the following:

• Certain important Amiga screens, such as alerts and the Early Startup Control screen, always appear in one of the 15 kHz modes, as do many games and certain other applications. A VGA-only monitor cannot properly display these screens.
• A 15 kHz-only monitor can display all system screens and virtually all Amiga applications, but cannot take advantage of Mode Promotion or the higher resolutions and enhanced displays that the AGA chip set offers.
• Vertical scan rates (also called the refresh rate) for display modes available under Release 3 vary from 48 to 73 Hz.

Check the specifications for a multiscan monitor carefully, however, as not all multiscan monitors accept 15 kHz input.

If you are not using a monitor that scans to 15 kHz, it is important to have your initial system settings made using a monitor that displays 15 kHz modes. Once your initial settings are made and you can use your regular monitor, you should make at least one backup floppy copy of your Workbench software containing these settings. If your ScreenMode editor display settings are accidentally changed, you can use this floppy disk to recover your display. Procedures for recovering a distorted display are described on page 7-15.

Required Scan Rates

The following sections group the monitors drivers according to the three basic horizontal scan rates that they require.

Video Monitors

Monitor Driver	Horizontal Scan Rate	Vertical Scan Rate
NTSC	15.72 kHz	60 Hz
PAL	15.60 kHz	50 Hz
Euro:36Hz	15.76 kHz	73 Hz

VGA Monitors

The standard VGA horizontal scan rate is 31.5 kHz. Most, but not all, VGA-only monitors can also display the 27 kHz promoted modes produced by the DBLNTSC and DBLPAL monitor drivers.

If your are attempting to use a VGA monitor with the DBL or Multiscan modes and it does not display those modes correctly, activating the VGAOnly monitor driver can help. It modifies the scan rates slightly to better match the VGA rates. However, this does cause the left edge of the screen to flash when scrolling horizontally, so you should not use VGAOnly unless it is necessary.

The next table shows the normal scan rate followed by the rates as modified by VGAOnly. If you activate or deactivate VGAOnly, you should delete the file ENVARC:Sys/overscan.prefs and reboot before editing your ScreenMode and Overscan Preferences settings.

Monitor Driver	Horizontal Scan Rates Normal/VGAOnly	Vertical Scan Rates Normal/VGAOnly
DBLNTSC	27.66 kHz / 29.30 kHz	58 Hz / 59 Hz
DBLPAL	27.50 kHz / 29.45 kHz	48 Hz /50 Hz
Euro:72Hz	29.32 kHz / 31.43 kHz	69 Hz / 70 Hz
Multiscan	29.29 kHz / 31.44 kHz	58 Hz / 60 Hz

Multiscan Monitors

A multiscan monitor can potentially display any of the previously listed rates, plus the following:

Monitor Driver	Horizontal Scan Rates	Vertical Scan Rates
Super72	23.21 kHz / 24.62 kHz	71 Hz / 72 Hz