On 14 Sep 99, at 13:19, Thomas Holmes wrote:

>   We have developed a feature comparison worksheet to analyze
> several competing proposals to upgrade some of our Win95 EtherNet
> workstations.  We intend to continue using our existing monitors.
> We noticed that some system configurations have a VGA connection
> and others have a SVGA connection.  At what point does a video
> system change from VGA to SVGA?  Are the I/O connections different
> and incompatible?  Should we find ourselves presented with a SVGA
> I/O connection, can we continue to use our existing VGA monitors?

  Vanilla VGA -- as it was defined in 1987 -- provides for 640x480
resolution and 16 colours.  Anything that provides higher resolution
and/or colour depth -- virtually everything made in the last decade --
 might be called SVGA: Super (enhanced) VGA.

  There are two ways that software can communicate with the video
adapter:  by manipulating controller registers on the card, or by
calling BIOS routines.  To the extent that there is an SVGA
"standard", it refers to a set of BIOS extension routines adopted by
VESA, an industry association of video-card makers.
  Many cards, since they provide a VESA SVGA BIOS interface, do not
completely/compatibly implement the full register interface as
defined by IBM, but this would only be an issue if you were running
code that tries to provide enhanced resolution or colour depth by
direct register manipulation; since you are running Win95, all of
your applications will rely on manufacturer-supplied drivers and so
this should not be any concern.

  VGA and SVGA monitors expect to receive an analog colour signal
vrom the video adapter.  Typically, a "VGA" monitor works properly
only with signals at a frequency that corresponds to 640x480 pixels
resolution.  While a few "SVGA" monitors accept only limited
variations from this (800x600, 1024x768), most are of the "MultiSync"
type, able to match frequency to the video card over a fairly broad
range.
  An SVGA video card *can* be configured to resolutions that a "VGA"
monitor can't display, but if your users stick to resolutions that
the monitor can handle, everything will work fine.

David G

                  Visit our website regularly for FAQs,
               articles, how-to's, tech tips and much more
                  http://nospin.com - http://nospin.org