Baslinux mailing list

["David Moberg" <davidjmoberg AT lycos.com>]

----- Original Message -----
From: "sindi keesan" <keesan AT sdf.lonestar.org>

> >> The result of all this was that xsvga is not working.
> >>
> >>
> >> SVGA:  WD (three lines about this - I have a WD video chip)
> >> SVGA:  chipset wd90c24 (it detected this)
> >> clocks :  28.32  28.32 .. (two lines of this)
> >
> > *red flag*! Only one dotclock rate is supported (28.32)?!
> 
> What is a dotclock?

VGA graphics cards only send out one pixel at a time to monitors.
This is because CRT monitors can only draw one pixel at any one
time. (Ask an electronics major if you want to know why this is
so.) The dot clock indicates the rate at which pixels are sent
out to the monitor. In your case, 28.32 million pixels are drawn
every second.

> I thought this looked odd but what does it mean?

Since your graphics card supports higher modes with an external
monitor (at least, I'm assuming that it does) this appears to
mean that the LCD will only accept one clock rate, and the
graphics card will not allow any others (to avoid LCD burnout).

So, we need to use a ModeLine which accomodates the needs of
this LCD.

> > Try this modeline. Add it with the others in the appropriate section
> > of XF86Config. Comment out the other 640x480 ones while you're at it.
> > This is 67.4 Hz, 33.7 KHz so you will need to adjust the range of
> > allowed sync ranges.
> 
> HorizSync 31.5-67.4?

HorizSync 30-40
VertSync 60-70

should do the trick.

> This is a range used by monitors that do 1280.

I meant a 67.4Hz vertical sync, 33.7 KHz horizontal sync. Horizontal
syncs are always in the KHz range, vertical is Hz.

> Is it the horiz or the vertical setting that can damage the monitor?

Both. Any incorrect modeline which makes it to the monitor will
cause damage. There are several things to prevent this from
happening:

1) XFree86 won't allow modes outside the HorizSync, VertSync, and
resolution settings which you have chosen.
2) Your graphics card may not allow bad modes (which is the case
here)
3) As a last resort, a good monitor will not allow incorrect
modes.

> Does Vertical Refresh mean the number of lines put on the screen in 
> one scan from top to bottom?

It means the number of times the electron beam of a CRT goes from top
to bottom (round-trip) each second.

> > Modeline  "640x480" 28.32   640  656  720  840 480 481 484 500 -hsync 
> > -vsync
> 
> I will try this tomorrow - the laptop computer has been put away 
> somewhere.  What do all the numbers here mean?  And the -hsync (or 
> +hsync, or lack of either)?  Maybe your website explains it.

I don't know what -hsync means.

> >> Thanks, I will use google to search on virtual screen and basiclinux.
> >
> > It would probably be easier to just browse through the April postings.
> 
> Okay, I have them in my inbox (1400 messages as of today).  I keep 
> meaning to go through and write down the useful parts but they get 
> ahead of me.

I was thinking that it would be easier to go to the BL list website,
and look throught the April threads.

David

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