vga.d

Name{number}
	vga - AdvanceCAB VGA Mode Remapper For DOS

Synopsis
	:vga [/l] [/u] [/a] [/c CONFIG] [/d] [/e]

Description
	The `vga' utility is a TSR (Terminate Stay Resident) VGA BIOS
	wrapper that substitutes the default list of VGA video modes
	with a list of the favorite modes which work best with your
	video hardware.

	The `vga.exe' executable can be used as a standard executable or
	it can also be loaded as a `sys' driver in the `config.sys' as a
	`device'. Please note that the `sys' version can't be unloaded.

	At the startup the configuration file `vga.rc', created with
	the utility `vgav', is read and all the modelines present
	are activated. The format of this configuration file is
	specified in the document `advv.txt'.

	These are some example rc files:

		ntsc.rc - NTSC TV.
		pal.rc - PAL TV.
		standard.rc - Arcade Standard Resolution (15 kHz).
		medium.rc - Arcade Medium Resolution (25 kHz).
		extended.rc - Arcade Extended Resolution (16.5 kHz).
		pcvga.rc - VGA PC Monitor.
		pcsvga60.rc - SVGA PC Multisync Monitor.
	
	From all the modelines in the configuration file three of them
	are chosen for the standard VGA mode 1h, 3h and 13h.

		1h - width of 40*9 or 40*8 pixel.
		3h - width of 80*9 or 80*8 pixel.
		13h - width of 320 pixel and height of 200.

	All the other modelines are used to adjust any other XMode
	detected. When the current video mode width and height match
	a modeline, the modeline is automatically set.

Options
	These are the command line options supported:

	/l
		Load in memory the utility and adjust the current video
		mode if a corresponding mode is defined in the config
		file.

	/u
		Unload the utility.

	/a
		Adjust the current video mode if a corresponding mode
		is defined in the config file without loading in memory
		the utility.

	/c CONFIG
		Use an arbitrary configuration file for the /l and /a
		commands.

	/d
		Disable all the video output from others programs.
		This option works only if the program is loaded in
		memory. Remember to reenable the video output before
		running your programs.

	/e
		Enable the video output.

	You can force a video mode reset in text mode using the standard
	DOS command:

		:mode co80

	or with the `video' utility.

Cards
	This utility should works with any VGA compatible board.

How It Works
	This utility intercepts all the VGA BIOS calls and if it detects
	a ModeSet call for a know mode it uses his version of the mode.

	At any call of the interrupt 08h and 21h some VGA registers are
	read. If a VGA mode with the size of a know modeline is detected
	the mode is adjusted to match the mode defined in the
	configuration file.

	The disabling of the video output works ignoring all the int
	10h calls.

Limitations
	Only the `modelines' compatible with the vga hardware are used.

	The text modes can use only the pixel clocks 28.322, 25.175,
	14.161 and 12.587 MHz. The graphics modes can use only the
	pixelclocks 14.161, 12.587, 7.080 and 6.293 MHz.

Examples
	Load it:

		:vga /l

	Load it with an arbitrary configuration file:

		:vga /l /c c:\myconf.rc

	Unload it:

		:vga /u

	Load it in the config.sys file:

		:device=c:\cab\vga.exe /l /c c:\cab\vga.rc

	Adjust the current video mode in the config.sys without loading
	in memory the utility:

		:device=c:\cab\vga.exe /a /c c:\cab\vga.rc

	Adjust the current video mode in the config.sys and disable
	all the video output:

		:device=c:\cab\vga.exe /l /d /c c:\cab\vga.rc

	the latter is probably the most interesting use. You can load
	`vga' as soon as possible to adjust the video output and prevent
	other programs to write to the screen. You can also use the
	`video' utility to load an arbitrary image to display.
	After the system is initialized you can insert in the autoexec.bat
	the command:

		:c:\cab\vga /e

	to reenable the video output.

Bugs
	The configuration file is checked only for the
	`device_video_modeline' options.
	All the other options are ignored.

Copyright
	This file is Copyright (C) 2003 Andrea Mazzoleni.