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On Wed, 21 Jul 1999 16:37:49 +0200, Marco Fioretti wrote:
> 2) Said this, allow me to show off my ignorance of the
> matter by asking what is the difference, if any, between
> sync_on_green and composyte sync features.

A monitor needs two sync signals: horizontal sync (hsync), and vertical
sync (vsync). When you combine hsync and vsync into one signal (can be
done with two 100 ohm resistors), you'll get a combined sync (csync)
signal. If you mix csync with the green signal, you'll get sync-on-green.

> I know that the X server for MATROX card will accept a
> sync_on_green option in the MONITOR section of XFREE86config,
> and I have seen "composite" is a valid flag at the end
> of a modeline, but are composite and sync_on_green
> mutually exclusive?

Yes they are, AFAIK. Also note that my S3 Trio64V+ accepts a sync_on_green
option, but it doesn't _make_ a sync-on-green signal. YMMV.

> Worst yet, since the SUN adapter may rewire signals internally,
> should'nt I just ignore the above options, and maybe
> just switch the hsync and/or vsync polarity ( from +vsync to -vsync,
> for example). Any idea?

Chances are high. The Sun monitor needs a csync signal, so it's possible
that the adapter makes it with two resistors:

VGA   -------------------> 13W3

hsync -->--[100R]--\
                    +----> csync
vsync -->--[100R]--/

Just use a multimeter and the connector pinouts available at
http://www.monitorworld.com/Cables/video_standards.html to find out. Or
simply open the adapter, if at all possible.

> Again, could any of the above fry the video card if set up wrongly?

I don't think you'll fry your monitor, as long as you switch it off (or
disconnect it) if you see that the video mode doesn't work. For the video
card: as long as you don't short-circuit the outputs, you should not be
able to fry it. With a little knowledge in electrical engineering and a
lot of common sense, you will be able to manage. No guarantees, however!


J.A.K. (Erik) Mouw, Information and Communication Theory Group, Department
of Electrical Engineering, Faculty of Information Technology and Systems,
Delft University of Technology, PO BOX 5031,  2600 GA Delft, The Netherlands
Phone: +31-15-2785859  Fax: +31-15-2781843  Email J.A.K.Mouw@its.tudelft.nl
WWW: http://www-ict.its.tudelft.nl/~erik/

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