    
OVERVIEW

    The VMODE utility allows the user to set horizontal and 
    vertical synchronization sent by the Ambra IVL graphics 
    system to the monitor. This utility controls the Tseng 
    LABS ET4000/W32p graphics controller which is integrated 
    on the IVL system mother board. This utility will only 
    function with TSENG based graphics controllers. The 
    instructions contained in this file refer only to the 
    AMBRA IVL system and not to third party add in cards. 

HORIZONTAL SCAN RATE:
    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 HORIZONTAL LINE is displayed (left 
    to right) is the horizontal scan rate. This is measured in 
    kilohertz, a unit of measurement that means one thousand 
    cycles per second. 

VERTICAL SCAN RATE OR REFRESH RATE:
    The vertical scan rate frequency, or refresh rate is the 
    period of time it takes to display one full screen (image 
    from top to bottom). This frequency is measured in Hertz (Hz) 
    a unit of measurement that means number of cycles per second. 
    The more times the screen is updated, (the higher the refresh 
    rate), the more stable the image on the screen appears to the 
    eye. A good example or demonstration of this is to run 
    windows at a resolution  of 1024 x 768 at 56Hz, and compare 
    this to a refresh rate of 70Hz. The image on the screen is 
    less pleasing and stable (appears to flicker) to the eye at 
    56Hz. The AMBRA IVL 486 can refresh the screen at 87 HZ 
    interlaced, 56Hz, 60Hz, 70Hz and 72Hz non-interlaced. If for 
    example you chose to refresh the screen at 72Hz, your display 
    would be updated at 72 times a second. The maximum refresh 
    rate that can be used is determined by the monitor and the 
    graphics sub-system on the AMBRA IVL 486.

INTERLACED Vs NON-INTERLACED:
    Interlaced is where it takes two passes to display the image 
    on the screen. The video is displayed on the screen in 
    horizontal lines, in interlaced mode odd lines are displayed 
    on the first pass and the even lines are displayed on the 
    second pass.  This results in the entire image being 
    displayed every second pass. The net effect of interlaced is 
    to half the refresh rate for example 87 Hz  interlaced is the 
    equivalent to 47.5 Hz non interlaced. 


USING VMODE:
    The VMODE utility is provided to aid in eliminating flicker 
    and other video distortion exhibited when monitors cannot 
    automatically synchronize to graphics frequencies of the IVL 
    486. By issuing one or more VMODE commands, you can improve 
    the display. VMODE commands can be issued from the DOS prompt,   
    added to your AUTOEXEC.BAT file, or incorporated into 
    separate batch files for starting applications that require 
    settings prior to loading. VMODE does not consume any of your 
    system memory. 

    Before using VMODE you must install the utility. To install 
    (setup) VMODE type the following at the DOS prompt:
	VMODE INSTALL
    You must then follow the instructions on screen and choose 
    whether your monitor is a variable frequency monitor or a fixed 
    frequency monitor.

    Before setting the modes below you must confirm what refresh rate 
    / resolution you monitor supports.

 
    At the MSDOS prompt type: VMODE <Value>

    VMODE       Vertical        Horizontal
    <Value>     Refresh Rate    Frequency       Resolution
     60HZ        60 Hz                          ALL RESOLUTIONS
     72HZ        72 Hz                          ALL RESOLUTIONS
     35K         56 Hz          35 KHz          800x600
     38K         60 Hz          38 KHz          800x600
     48K         72.7 Hz        48.4 KHz        800x600
     45M         86.5Hz I       35.5 KHz        1024x768 *
     65M         60.5 Hz        48.9 KHz        1024x768 
     72m         69.8 Hz        56.3 KHz        1024x768

    * Interlaced

Note: Choosing VMODE 60HZ will return the graphics sub-system to 
      normal (standard) operation.

EXAMPLES:

	       (WINN.BAT)
		VMODE 35K
		WIN
     This batch file sets the 800 x 600 resolution to a 56Hz refresh rate

	     VMODE 72
     The command above sets all resolutions to 72Hz

	    VMODE 45M
     This command sets the 1024 x 768 resolution to 87Hz interlaced.

AMBRA MONITORS:
     The following table list the maximum refresh rate for the standard 
     resolutions for each Ambra Monitor.

AMBRA MONITOR   SIZE    640 x 480     800 x 600     1024 x 768   1280 x 1024
----------------------------------------------------------------------------
VGA             14"        60Hz          56Hz           87Hz I
SVHA & SVGA LR  14"        60Hz          56Hz           87Hz I
UVGA LR         14"        72Hz          72Hz           72Hz
15" MPR-II      15"        72Hz          72Hz           73Hz
17" MPR-II      17"        72Hz          72Hz           73Hz         60Hz
		

