Baslinux mailing list

[sindi keesan <keesan AT sdf.lonestar.org>]

On Thu, 12 May 2005, David Moberg wrote:

> ----- 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).

Yes, there is an external video output, which I think lets you do 800x600 
on a CRT.  I remarked out all the 800x600 parts in the config file.

> 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.

I tried HorizSync 33.7 and also 35.36, and VertRefresh 67.36, as suggested 
by one of your websites.  I tried your suggested modeline and also the 
modeline posted at both sites you referred to.  Your modeline got me the 
error messages:  Fatal server error:  Dotclock expected.


I tried filling in a Clocks line as suggested at one website, with 17 
copies of 28.32 and one of 49.84 (which svga also detected).  I tried 
without this.  Same result.

I tried the modeline from the two websites and it got me farther but there 
was still the error message about no mode definition named "640x480".
I removed anything for higher modes than this, and all devices besides 
svga (took out accel, vga, mono).

Now I tried with the range you suggested and got something about 
resolution too large for virtual mode 320, so I remarked that out too 
(xf86config must have put it in).

Progress!  (Using the modeline from the websites, which does not tell me 
Dotclock expected, and the Clocks line is back).

error opening security policy file 
/usr/X11R6/lib/X11/xserver/SecurityPolicy  (all on one line)

I got this one time earlier with the vga or maybe the mono server.  I 
don't even have /usr/X11R6/lib/X11.  Perhaps this file needs to be added 
from somewhere (in Steven's little no-xvesa.tgz package).  I can't figure 
this out from a websearch - what does security have to do with X_SVGA? 
The server worked with three other video chips.

> > 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.

Why did setting a range work, when setting the exact frequencies did not? 
I notice you said 67.4 and someone else 67.36.

> 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.
Can an LCD monitor be damaged by the wrong 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.

67 times per second. 
This monitor or chip is also 60Hz - what is that measuring?

> > > Modeline  "640x480" 28.32   640  656  720  840 480 481 484 500 -hsync -vsync

This did not work but the one from the websites did:
Model "640x480" 28.32 640 664 760 800 480 491 493 525  (no -hsync)


My TTL monitor was once damaged by sending it VGA frequencies - I was 
playing with a little Thai wordprocessor and forgot to switch to VGA first 
and the program was not written  to check for TTL.  A $2 part fixed it.